This thesis presents and discusses the development, design and testing of a lightweight current pulse source prototype used for condition assessment of line connectors. The thesis is a continuation of a student project conducted in the fall semester of 2014 with the title "Condition Assessment of Line Connectors by Current Pulse Measurements - Effect of Reduced Pulse Rise Time And Connection Cable Cross Section". The student project looked into how weight and size could be removed from the present pulse source design, both by a reduced capacitor bank and by reduced connection cable cross section. The results from this project lead to the development of the lightweight pulse source prototype.The design and development is divided into three sections. Initially, the overall idea and generalization of the design is presented and discussed. Secondly, based on this conceptualization the design is broken down to each major component. These components were the battery, thyristor, capacitor bank, microcontroller, DC-DC Converter, and user interface. Their function and design criteria are presented and discussed in the thesis. The thesis also presents the circuit schematics of all the components designed specially for the prototype. Finally, the design is summarized and its weight and size compared to the present pulse source design. The measurements show that new pulse source prototype weights 7.6 kg compared to the 35 kg of the old design and is 47 dm^3 smaller. Note that the weight is measured without the connection cords and measurement equipment. enlargethispage{baselineskip}One of the major differences beside the size and weight is that the present pulse source uses a hardware based sequence control, while the prototype utilizes a microcontroller. This allows a much more flexible system since the behavior of the sequence control can be altered by rewriting the script. The microcontroller and script are presented in detail in the thesis and in the appendix.To verify the design, and to look into how the prototype operates during actual condition assessment measurements, a total of thirteen connectors were assessed. Three of these had an already known condition, while for the rest no prior condition assessment existed. The three connectors with a known state showed that it was possible to reproduce the results from the prior measurements using the pulse source prototype. The ten final connectors were meant to increase the number of measurements to see how the prototype handled during actual assessment tests. These measurements show that the prototype only needed a few alterations to it design to operate satisfactory. These alterations are presented and discussed in the thesis, while the condition assessment of all the connectors is presented in the appendix.In addition to the condition assessment measurements there were also conducted two separate experiments to define the battery capacity and setpoint accuracy of the prototype. The battery capacity test revealed that the battery capacity of the prototype is sufficiently large to supply the unit with power during continuous operation for at least four hours and ten minutes, and deliver 500 consecutive shots. The setpoint accuracy test indicated that the prototype's control sequence was able to reproduce the same current amplitude for the same setpoint with a deviation of only 26.4 A.All the tests performed on the prototype show that it works and operates as intended. Tests have shown that the prototype is able to produce and reproduce current pulses accurately up to and above 6000 A, and that the microcontroller based sequence control functions as intended.

Permanent Magnet (PM) machines can have difficulties dealing with unstable loads, which in worst case can make the machine to step-out of synchronous speed. This problem can be avoided by equipping the rotor with damper windings. During load variation the damper winding will induce a torque to dampen the impact of the load variation. To investigate the effects from using damper windings a numerical model of a PM machine was developed and studied in this thesis. The model is intended to operate with regards to load torque and the stator field. The stator configuration which was used in this thesis is very complex, which resulted in a lot of trial and error. Due to the complexity of the stator meant it had to be applied with a current density, which means that the voltage over the phases was not taken into account during the simulations. This simplification appears to have created an unnatural damping factor in the simulations.Simulations show that a high-conductive damper winding performs faster during load variations then a low conductive damper winding. The reason for this is that a low resistance will induce a high torque at low slip. The size of the windings also affects the performance but these are small and difficult to notice. Simulations show that the size of the damper winding should be between 5-10% of the size of the stator winding.

The conventional electrical system in place today sees our electrical devices powered by AC mains. But as renewable technologies such as solar photovoltaic and wind power become more prevalent at a household level, DC micro-grids could be a cheaper and more efficient alternative. New lighting devices (LED) can reduce the electricity consumption substantially. Two alternatives are envisioned in this paper: A stand-alone alternative in which there is no grid connection, that would require local storage (battery), and a grid-connection alternative. After reviewing and investigating relevant literature for this topic and writing theoretical part of thesis there were the fallowing tasks. One typical four member family household was described and hourly load curves for one year period, with typical summer and winter days, were made for this case. Next task that was completed was generating yearly energy production from solar panels, which the observed household contains, in INSEL software. With having those previously mentioned data, combined with necessary information about prices of all necessary components and prices from Croatian power system, it was possible to make feasibility and cost analysis where the two previously mentioned alternatives were investigated. With changing some parameters in that economical analysis several scenarios were observed. At the end conclusions were made about which one of those two options is more profitable and under what conditions. Also, suggestions were made for further work on this topic. This assignment is realized as a part of the collaborative project “Sustainable Energy and Environment in Western Balkans” that aims to develop and establish five new internationally recognized MSc study programs for the field of “Sustainable Energy and Environment”, one at each of the five collaborating universities in three different WB countries. The project is funded through the Norwegian Programme in Higher Education, Research and Development in the Western Balkans, Programme 3: Energy Sector (HERD Energy) for the period 2011-2014.

<p>Följande rapport beskriver ett projektarbete i att ersätta en automatisk spännings regulator (AVR) till en gammal ASEA dieselgeneratoranläggning. Generatorn är installerad på M/S Calmare Nyckel som tillhör Sjöfartshögskolan i Kalmar. Generatoranläggningen används enbart i utbildningssyfte.</p><p>Den AVR som ska ersättas är en ASEA UTWH310. Det är ett väldigt gammal anläggning och vi uppskattar att den härstammar från 60-talet. Problemet med den gamla regulatorn är att när systemet har körts en stund så är det inte längre möjligt att reglera den reaktiva effekten. Vi blev tillfrågade att ersätta det gamla systemet, därför har vi inte gjort något försök att laga det.</p><p>Regulatorn matar ström till en liten DC generator, mataren, som är ansluten till den större AC generatorn med remdrift. Mataren magnetiserar sedan rotorn i AC generatorn. För att få klarhet i hur systemet fungerade så gjorde vi några testkörningar. Vi tog reda på nödvändiga parametrar för att kunna ersätta den gamla anläggningen.</p><p>Eftersom vi inte hade någon tidigare erfarenhet av den här typen av projekt, så hade vi lite problem att hitta en leverantör av den nya AVR utrustningen. Som tur var kom vi i kontakt med Subtron AB, ett litet företag från Enköping. De var mycket hjälpsamma, och de hade både kunskapen och utrustningen som vi behövde.</p><p>Vi beslutade oss för att beställa Leroy-Somers R 448 AVR. Det är en enkel AVR men fullt kapabel att utföra det vi efterfrågar. Vi beställde också en del kringutrustning till installationen. Efter att ha testkört den nya utrustningen och kommit fram till att den fungerade utmärkt så utfördes installationen sedan på några dagar.</p> / <p>This following report describes a project in replacing the Automatic Voltage Regulator (AVR) in an old ASEA diesel generator system. The generator is installed on M/S Calmare Nyckel which belongs to Kalmar Maritime Academy. The Generator system is solely used for educational purposes.</p><p>The AVR that is being replaced is an ASEA UTWH310. It is a very old system and we assume its from some where around 1960. The problem with the old AVR is that when the system has been running for a while there is no longer possible to control the reactive power. We were asked to replace the old system, so not much effort has been put on trying to repair it.</p><p>The AVR feeds current to a small DC generator, feeder, witch is connected by a strap drive to the larger AC generator. The feeder then excites the rotor in the AC generator. To find out how the system actually worked we made some test runs. We measured necessary variables to be able to replace the old system.</p><p>Because we had no formerly experience in this type of project, we had some troubles in finding a supplier of AVR equipment. Luckily we came in contact with a small company called Subtron AB from Enköping. They were very helpful and had both the equipments and the knowledge that we needed for our project.</p><p>We decided to order Leroy-Somers R 448 AVR. It is a simple but fully capable AVR to preform what we asked for. We also ordered some auxiliary equipment for the installation. After a test run with the new equipment, we found out that it worked very well. The installation process was then made in a few days.</p>

Examensarbetet har utförts på uppdrag av NEA Gruppen och är en elkvalitetsanalys av VBG Groups maskinhall. Målet med analysen var att uppvisa elkvaliteten i maskinhallen. Perfekt elkvalitet kan definieras som total frånvaro av elektriska störningar. Av elektriska störningar är det framförallt spänningsstörningar, såsom kortvariga spänningsvariationer, spänningsosymmetrier, spänningstransienter och likspänningskomponnenter, som orsakar mest besvär för elnät och anslutna laster. Även övertoner, som kan delas i spännings- och strömövertoner, påverkar elsystem på ett negativt sätt. Analysen visar att maskinhallens spänning är stabil. Detta var väntat då kortslutningseffekten är hög jämfört med anläggningens storlek. Det matande nätet kan alltså anses starkt. Maskinhallens laster alstrar strömövertoner av framförallt ordningstalen 5 och 7 men eftersom det matande nätet är starkt ger dessa inte upphov till några spänningsövertoner som ligger utanför rekommenderade gränser. I maskinhallens ena inmatningspunkt, T1A15, finns ett kondensatorbatteri anslutet för reaktiv effektkompensering. Vid den andra inmatningspunkten, transformatorstation T3, finns idag ingen kompenseringsutrustning. Behovet är inte heller stort då belastningsgraden av T3 idag är under 10%. Man kan dock se att den reaktiva effekten redan nu är lika stor som den aktiva vilket medför att effektfaktorn är ca 0,7 och inom en nära framtid kommer fler laster att anslutas till T3 vilket innebär att ett kondensatorbatteri kan vara en lönsam investering. Maskinhallens belysning alstrar strömövertoner av framförallt ordningstal tre. Övertoner av detta ordningstal har egenskapen att de ger upphov till strömmar i neutralledaren, i värsta fall så stora att neutralledaren blir överbelastad. Någon risk för överbelastning av neutralledaren för maskinhallens belysningsgrupp finns dock inte. Totalt sett är anläggningens elkvalitet god och inga akuta åtgärder behöver vidtas.

Det finns inom Vattenfall Eldistribution AB ett intresse att automatisera felsökning i elnätet. Syftet med detta examensarbete är att utreda möjligheten att utplacera feldetektorer i Vänersborgs centrala elnät. Ett förslag på en optimal placering av feldetektorerna utifrån ett tekniskt och ekonomiskt perspektiv presenteras. Den föreslagna placeringen av feldetektorer bygger på det befintliga signalkabelsystems struktur. Signalkabelsystemet för Vänersborgs centralort finns dokumenterat i Vattenfalls dokumentationssystem. Samhällskostnader har beräknats och sammanställts för berörda ledningar. I beräkningsmodellen har olika alternativ med utplacerade feldetektorer simulerats. Alternativen utvärderas därefter i relation till felsökningstid, felfrekvens och samhällskostnad. Med framtagen beräkningsmodell erhålls samhällskostnaden för varje ledning, för ett genomsnittligt avbrott. Beräkningsmodellen visar även hur samhällskostnaden reduceras vid alternativa utplaceringar av feldetektorer. För det optimala alternativet med utplacerade feldetektorer i Vänersborgs centralort har den reducerade samhällskostnaden ställts i relation till investeringskostnaden. Därefter har den ekonomiska besparingen kunnat fastställas. Det har visat sig enligt detta examensarbete, att det med avseende på samhällskostnader och kundnytta är en bra investering att installera feldetektorer. Med den föreslagna optimala placeringen av feldetektorer, passeras återbetalningstiden för investeringen efter sex till sju år. Det genererar samtidigt en förhöjd kundnytta. Ett minskat antal provinkopplingar medför dessutom att kablar och elapparater inte på samma vis utsätts för höga kortslutningsströmmar, vilket resulterar i en längre livslängd för elnätet.

With an ongoing desire to improve product performance, in combination with the continuously growing complexity of engineering structures, there is a need for well-tested and reliable engineering tools that can aid the decision making and facilitate an efficient and effective product development. The technical assessment of the dynamic characteristics of mechanical systems often relies on linear analysis techniques which are well developed and generally accepted. However, sometimes the errors due to linearization are too large to be acceptable, making it necessary to take nonlinear effects into account. Many existing analysis techniques for nonlinear mechanical systems build on the assumption that the input excitation of the system is periodic and deterministic. This often results in highly inefficient analysis procedures when nonlinear mechanical systems are studied in a non-deterministic environment where the excitation of the system is stochastic. The aim of this thesis is to develop and validate new efficient analysis methods for the theoretical and experimental study of nonlinear mechanical systems under stochastic excitation, with emphasis on two specific problem areas; forced response simulation and system identification from measurement data. A fundamental concept in the presented methodology is to model the nonlinearities as external forces acting on an underlying linear system, and thereby making it possible to use much of the linear theories for simulation and identification. The developed simulation methods utilize a digital filter to achieve a stable and condensed representation of the linear subparts of the system which is then solved recursively at each time step together with the counteracting nonlinear forces. The result is computationally efficient simulation routines, which are particularly suitable for performance predictions when the input excitation consist of long segments of discrete data representing a realization of the stochastic excitation of the system. Similarly, the presented identification methods take advantage of linear Multiple-Input-Multiple-Output theories for random data by using the measured responses to create artificial inputs which can separate the linear system from the nonlinear parameters. The developed methods have been tested with extensive numerical simulations and with experimental test rigs with promising results. Furthermore, an industrial case study of a wave energy converter, with nonlinear characteristics, has been carried out and an analysis procedure capable of evaluating the performance of the system in non-deterministic ocean waves is presented.

<p>This thesis investigates simulation of synchronous machines using a novel Magnetic Equivalent Circuit (MEC) model. The proposed model offers sufficient detail richness for design calculations, while still keeping the simulation time acceptably short.</p><p>Different modeling methods and circuit alternatives are considered. The selected approach is a combination of several previous methods added with some new features. A detailed description of the new model is given. The flux derivative is chosen as the magnetic flow variable which enables a description with standard circuit elements. The model is implemented in dq-coordinates to reduce complexity and simulation time. A new method to reflect winding harmonics is introduced.</p><p>Extensive measurements have been made to estimate the traditional dq-model parameters. These in combination with analytical calculations are used to determine the parameters for the new MEC model.</p><p>The model is implemented using the Dymola simulation program. The results are evaluated by comparison with measurements and FEM simulations. Three different operation cases are investigated; synchronous operation, asynchronous start and inverter fed operation. The agreement with measurements and FEM simulations varies, but it is believed that it can be improved by more work on the parameter determination.</p><p>The overall conclusion is that the MEC method is a useful approach for detailed simulation of synchronous machines. It enables proper modeling of magnetic saturation, and promises sufficiently detailed results to enable accurate loss calculations. However, the experience is that the complexity of the circuits should be kept at a reasonable low level. It is believed that the practical problems with model structure, parameter determination and the simulation itself will otherwise be difficult to master.</p>

The main performance objective in an electric power grid entails timely and efficient generation and delivery to the time-varying electricity demand. As the electricity industry is witnessing proliferation of the mainstream renewables, the minute-by-minute variations in wind and solar power generation may result in temporary electricity scarcity that jeopardizes grid stability and quality of service. The evolving electricity markets are aimed at incentivizing the conventional generators to reinforce their operating flexibility. This dissertation concerns the goal of enhancing the dynamic response rates of interconnected controllable resources by means of a multi-layered fuel input control of electrically coupled heterogeneous energy conversion components. Both power engineering and large-scale control contributions are made in support of this enhancement. First, improved fuel input controls are designed to enable flexible physics-based energy conversion dynamics required by the interconnected grid. To efficiently utilize the resources load-following and regulation problems are stated. The efficacy of proposed fuel input control designs in enhancing the dynamic response rates is illustrated on IEEE 14-bus system. Second, the problem is formalized as multi-input multioutput time-varying trajectory tracking based on a decentralized spatiotemporal composite control design. The concepts of vector-Lyapunov function and singular perturbation are invoked to formalize model decompositions, over space and time, respectively. Next, the assumptions for model simplifications are relaxed and the problem of parametric uncertainty is addressed. A minimumcost resilient co-design approach is introduced for storage-sensors-communication channels in a complex electric power grid. The notion of selective strong structural fixed modes is explored as a characterization of feasible decentralized control laws for an arbitrary system realization satisfying a pre-specified structure. Finally, it is proposed that planning of generation portfolio must be driven by the objective of maintaining adequate operating flexibility in the system. The goal is to ensure sufficient ramp capacity to sustain the significant integration of intermittent renewable resources.

The aim of this diploma thesis is to highlight in theoretical and practical level the possibilities and opportunities as well as risks and threats to enter the Chinese market for business or commercial enterprises. Framework of the first part - SWOT analysis of the Chinese market - was designed according to information provided by individual companies actually exporting to the Chinese market. This section is devoted to monetary and fiscal policy and analysis of consumer demand, the tax system in China, protection of intellectual property rights or the issue of corruption, bureaucracy and the Chinese state-owned enterprises. Subsequently there are examples of three companies - Skoda Power and Skoda Transportation and Skoda JS - operating for several years on the Chinese market. Each company chose different way of entering this market and the aim was to analyze these approaches in terms of financial and legislative expediency. The last part of the paper is devoted to vision and analysis of emerging perspective industries and energy.