<p>The work consists in developing a power conversion unit for solar panel connected to the grid. This unit will be a single phase inverter in the low power range (24/48 V - 100/200 W), with digital control and without a DC-DC stage. The final system should be suitable for laboratory work. This master project will be complete, starting with a detailed specification of the project and finishing with an experimental validation.</p>

<p>Characterization of Epoxy (diglycidyl ether of Bis-phenol A cured with Tri ethylene Tetra amine) without fillers was done. The Water absorption test at 95°C shows that at saturation the epoxy contains a water concentration of 2.089%. The diffusion coefficient of absorption is calculated as 0.021 cm2/s. The diffusion coefficient of desorption is calculated as 0.0987 cm2/s. The diffusion is almost 5 times faster than absorption. Also the material looses weight as the hydrothermal aging progresses. The water in the sample leads to chain scission which leads to the weight loss. The weight loss is more incase of absorption followed by desorption than only absorption. The chain scission leads to decrease in the mechanical strength by around 45%. The diffusion of water from the samples doesn’t affect the mechanical strength of the materials. The glass transition temperature reduces by 20°C with water inside the sample. The diffusion of water out of the sample only increases by around 10°C. The Dielectric response of the material shows that after the water absorption the sample shows high losses at lower frequencies. Also the increase in the real part of the permittivity increases with low frequency. The rapid increase in the real art of the permittivity of the material at lower frequencies can be attributed to a polarization at the electrode due both to accumulation of the charge carriers and to chain migrations. The breakdown test of the samples shows that with water in the sample the breakdown strength of the material decreases by 10 KV, but the material regains its dielectric strength when the water is diffused out. This shows that the chain scission and weight loss of the samples has no or minimum effect on the dielectric strength of the sample</p>

<p>This report is divided into six main chapters. It starts off with an introductory chapter explaining the different propulsion strategies that have been considered during the last semester, and the final propulsion system that has been decided upon. The final propulsion strategy has several demands when it comes to components that have to be implemented and what type of components they should be. The main purpose for me in this project was therefore to meet these demands. Main demands for me were to demonstrate different possibilities when it comes to controlling the lights in the PureChoice vehicle, and to make sure the vehicle had enough energy stored in alternative storage devices in order to have a fully functioning system when it comes to driving the vehicle and managing the safety system onboard. The report continues with five individual chapters explaining how these demands were solved and which components that have been considered and implemented in the final vehicle. All off the chapters start of with an introduction about the topic at hand. They then continue with an explanation about the different components used in the vehicle, and reasoning for why exactly these components were chosen. In order to determine how the components would function in the final propulsion system, laboratory tests were performed on all the involved parts, and these laboratory tests are described at the end of all the chapters. This report includes both theoretical calculations and practical solutions.</p>

<p>Summary Literatures on battery technologies and diagnosis of its parameters were studied. The innovative battery technologies from basic knowledge to world standard testing procedures were analysed and discussed in the report. The established battery test station and flowchart was followed during the battery test preparation and testing. In order to understand and verify the battery performance, the well established test procedures developed by USABC (United States Advanced Battery Consortium) and FreedomCAR were reviewed. Based on the standard battery test flow diagram, battery test procedures are mainly categorised as below; 1. Test plan and pre-test – readiness review 2. Core performance test – charging, discharging, power, capacity and other special tests 3. Life cycle/ageing test – accelerated ageing, calendar life, abuse and safety Commercial battery testers were used to carryout the core performance test but electrochemical impedance spectroscopy (EIS) was employed for life cycle test and also to investigate the state of health (SOH) and state of charge (SOC) of the battery. The standard test bench as shown below was used for the experiment under the scope of this thesis. Figure 1: Standard battery test station Study on impedance based modelling of battery and laboratory experiment to measure the impedance was carried out. Electrochemical impedance was measured by applying an AC potential to an electrochemical cell and measuring the current through the cell using the shunt in series where battery voltage was measured directly from the terminals as shown in figure 1.Commercially available battery sensors were used to measure the current, voltage and temperatures. Impedance was calculated internally and observed on computer through the battery test program and also observed on Nyquest plot where real part is plotted on the X-axis and imaginary part on Y-axis at one frequency. A typical impedance spectrum of a Li-ion battery tested in the laboratory at 250C is presented below. This figure shows the measured impedance for different state of charge (SOC) without dc excitation current. Figure 2: Impedance Spectra of a Li-ion battery At real impedance Re(Z)  42 m, the real axis intersection of the impedance spectra was observed in the figure 2. For lower frequencies, all spectra show two semicircles. The first semicircle is comparably small and slightly depressed, whereas the second one is larger, nearly non-depressed and grows remarkably with decreasing state of charge. Finally, at the low-frequency end of the depicted spectra, the diffusion impedance becomes visible. At high states of charge, the diffusion impedance shows a 45°-slope, which is typical of Warburg impedance (state of diffusion at certain frequency).</p>

<p>Power system simulations, power market analysis as well as power system security and reliability analysis now serves as fundamental analysis tasks in power system planning and operation. Thus, it is very useful to discuss techniques, data needs and methodologies related power system reliability. Work is very important both in terms of operational and economical aspects of a modern power system. The task of determining the reliability of a given power system can be a complex and difficult process. Several methodologies exist and the terminology describing these calculations may differ from case to case. The work performed in this thesis demonstrates a known reliability methodology related to a real-life power system. In the latter, PSS®SINCAL and its reliability module ZUBER has been emphasized. The development of a working test model has been an important part of this thesis. In the latter, statistical information describing the power system has been the main challenge, both in terms of availability and quality. The various reliability data have been calculated from annual failure statistics collected by Statnett and experience data from Siemens. The scope of the reliability analysis was to determine the affect of future load expansions. It is a known fact that load development can affect the reliability of the power system and potentially increase the frequency of supply interruptions causing higher CENS costs. However, this was not the case as the changes in frequency of supply interruptions were insignificant. The results showed a suspected CENS cost increase of 1.6 NOK. Thus, it is evident that this is due to the fact that the uninterrupted power is now substantially larger. The reliability analysis show that the given power system will sustain its high level of reliability even with the planned load expansion. A comparative analysis of the ongoing development of a methodology (SAMREL) incorporating power market analysis via power flow and contingency analysis and PSS®SINCAL have also been presented. Comparing tools describing probabilistic reliability are important and can act as an incentive for future development of reliability tools. The major strength of PSS®SINCAL compared to SAMREL is simply the fact that PSS®SINCAL is a developed and commercialized tool. Unfortunately it was not possible conduct a reliability analysis using SAMREL, which was a major draw-back as a comparative analysis of both the tools relates to the same test model would have been very beneficial. SAMREL is comprised of several existing tools and therefore rely on the interaction between these tools, which after my opinion further complicate both the user friendliness and process of commercialization. From an educational point-of-view, the work related to SAMREL has several benefits contributing to increased general knowledge about power system reliability. It is evident that the accuracy of any reliability analysis depends on the quality of the statistical data. The studies show that local statistical data e.g. data based on local knowledge or local statistics often pose as a better solution. However, such data are unfortunately often very difficult to obtain, leaving no alternative as to use the available more general data. However, it is evident that some uncertainties always will exist but need to be taken into consideration when conducting such analysis. However, close cooperation with the utilities in combination with the utilization of high quality reliability data will after my opinion have a positive affect on the accuracy of the reliability analysis. Another important subject related to reliability is the process of identifying the critical system components. As shown, the main tool presented in this thesis is the consequence matrix, which categories the results obtained from the reliability analysis. The categories indicate both the consequence and the corresponding probability. Such matrixes need to be the result of a joint effort from both the customer and the professionals performing the criticality analysis, including all relevant information needed to classify criticality. The strength of this method lies in the fact that the defined probabilities can be used to identify large elements, such as substations and then be further utilized on a component level for the critical substation. The methodologies describing power system reliability have been emphasized throughout this thesis. The given test system and the performed reliability calculation demonstrates PSS®SINCAL as a tool for determining the reliability of a power system. The methodology utilized in this report is from the author’s point of view a good representation of a state of the art reliability analysis.</p>

<p>In the last decades, due to the environmental concerns and the increase of energy demand, wind power has strongly penetrated the field of electricity generation. Today, because of the lack of onshore sites and visual and noise nuisances, the development of wind farms turns more and more to offshore and Norway has a great potential of offshore wind power. This thesis investigates the impact of the integration of an offshore 1000MW wind farm on the Norwegian power system. Two different transmissions are used, one HVAC transmission system and one HVDC transmission system. They are installed in four different configurations which represent the possible cases of wind farm integration regarding the distance from the shore. Two different connection points have been chosen regarding the load flow simulations. The first one is situated in the region of Bergen in the West Norway and the other one is situated between Kristiansand and Stavanger in the south Norway. In order to investigate the power stability and the behaviour of the system, simulations are performed under both steady-state and dynamic conditions by using PSSTME. Disturbances are applied in different locations on the system both near the connection point and on the offshore wind farm. The results show that the power system with large offshore wind power remains stable after the different faults. The requirements of the Norwegian Transmission System Operator, Statnett, are respected after the integration of a large offshore wind farm in the Norwegian power system.</p>

<p>A stable and reliable electric power supply system is an inevitable pre-requisite for the technological and economic growth of any nation. Due to this, utilities must strive and ensure that the customer’s reliability requirements are met and the regulators requirements satisfied at the lowest possible cost. It is known fact around the world that 90% of the of the customer service interruptions are caused due to failure in distribution system. Therefore, it is worth considering reliability worth assessments as it provides an opportunity to incorporate the cost or losses incurred by the utilities customer as a result of power failure and this must be considered in planning and operating practices. The system modeling and simulation study is carried out on one of the district’s distribution system which consists of 33kV and 11kV network in Bhutan. The reliability assessment is done on both 11 and 33kV system to assess the performance of the present system and also predictive reliability analysis for the future system considering load growth and system expansion. The alternative which gives low SAIDI, SAIFI and minimum breakeven costs are being assessed and considered. The reliability of 33kV system could be further improved by installation of load break switch, auto recloser and connecting with line coming from other district (reserve) at reasonable break even cost. The decision base could be further improved by having Bhutan’s context interruption cost. However, the questionnaire’s which may be used in Bhutan to acquire interruption costs from the customers are being proposed. The utility should have their own reliability improvement strategy depending upon their needs and requirements of the regulators. Although there is no magic bullet in managing power quality issues, utilities can maximize network performance and better serve customers by diligently addressing trouble prone areas. In order to achieve this objective, a computer program NetBas/Lesvik is used to run load flow and reliability analysis, thus selecting the alternatives either based on reliability indices or on cost benefit ratio.</p>

<p>The thermal behaviour of an IGBT module was investigated, especially with respect to the module being immersed in dielectric oil. An equivalent thermal model was built using thermal transients and network synthesis. The thermal behaviour was further investigated using thermocamera measurements and simple finite element models. Passive pressure testing of electronic components relevant for the test setup was performed. The testing showed no significant influence on the electrical behaviour of the components. An IGBT module without gel covering the chips was switched while immersed in dielectric oil. The switching transients were compared to the case of a normal module switching in air. Only minor differences were found between the switching waveforms from the two cases. A test was performed where water was added to the dielectric oil in order to reduce the breakdown voltage of the oil. No breakdown phenomena were observed for the voltages that were tested. A brief litterature study regarding stray inductance considerations in the test setup was performed.</p>

<p>This thesis studied reliability of power supply in Zambia following two major power blackouts that affected the whole country. The case study focussed on the generation and transmission network owned by Zambia’s biggest utility company Zesco. Three methods of study were selected. The first method looked at the transient stability simulations of Zesco generators when subjected to a large disturbance after a three phase short circuit was applied at three selected buses which are considered critical to the system. The simulations were carried out in SIMPOW. The results show that with fault duration of less than 200 milliseconds, all generators regained synchronism after fault removal. However, extending the fault duration to 200 milliseconds resulted in loss of synchronism in generators at Victoria Falls power station. The second method studied the contingency of some critical components in the Zesco system. The contingency analysis was implemented using software called NETBAS. Study showed that the Zesco system is N-1 stable for contingencies involving transmission lines and transformers. However the system is vulnerable to contingencies involving major power stations such as Kafue gorge and Kariba North bank. The third study proposed modification to the distance protection system to include the effect of zero sequence mutual coupling resulting from parallel circuits following a fault involving earth on a protected line. Adaptive techniques were developed where the settings of the distance relay would change to suit the circuit configuration. This technique resulted in optimal performance of the distance relay under all conditions of parallel line operation. The thesis concludes by making recommendations based on the findings from the studies carried out.</p>

<p>Norway and the EU have in recent years established ambitious goals to increase the share of renewable energy in their consumption. On account of these goals, a large-scale wind power development can be expected in northern Norway and Sweden. This development may be financed both by Norway and by countries with less wind resources in order to meet the energy goals imposed upon them. An increased power surplus is dependent on TSOs' abilities to transmit increased amounts of power through the Nordic grid. A scenario of likely power market conditions in year 2025 is used as a basis. The scenario has a high expectancy of new wind power as well as strong grid investments compared to the level in 2009. This thesis assumes an additional increase in annual renewable power production of 22 TWh, divided into 16 TWh in northern Norway and 6 TWh in northern Sweden. Results show that this amount of new power cannot be implemented without large grid investments. The Energy and Power Flow model is utlized to simulate the Nordic power flow for different levels of grid investments. Two grid solutions are proposed that allow the production increase while maintaining an acceptable state of system operation. The first uses DC transmission from Rana to Oslo in order to control power flow through Norway. An additional AC line from Kobbelv to Ritsem allows import from Sweden to the DC line. The second grid solution uses AC line upgrades throughout Norway ensuring two 420 kV lines from Ofoten to Kristiansand. Due to lower impedances in the Swedish grid, a large amount of the Norwegian production flows into and through Sweden. This solution requires a new line from Kobbelv to Ritsem and Rätan to Borgvik in order to solve resulting Swedish transmission congestion. Both grid solutions require a new DC cable from southern Norway to Germany in order to export most of the new power production. These cables require a number of supporting line upgrades in the region. Power producers schedule according to the new market situation, allowing a very high export during daytime and a low export during night. The increased power production in northern Norway and Sweden replaces other production. A high amount of gas and coal power is replaced in continental Europe. No hydropower, wind power or nuclear power is replaced. The DC and AC grid solutions allow European reductions corresponding to 19,3 % and 16,6 %, respectively, of the expected Norwegian CO2 – emissions in year 2025. The cost of each grid solution is calculated to 22 760 MNOK and 19 310 MNOK. Annual system increases in valued socio-economic benefit outweigh the grid investment costs of each option by 3 300 MNOK and 3 370 MNOK per year of the period of analysis. The total cost of new power production must not exceed these values for such a decision to be socio-economically beneficial. Due to the high increases in calculated socio-economic benefit, a recommendation for further analysis is made.</p>