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The environmental awareness has led to many political decisions and initiated laws that regulate the market towards responsible energy usage. The demand of sustainable power has led to an increasing integration of renewable energy sources to the electric grid. Solar power is the 3rd largest renewable power source after wind and bio-power. One of the main reasons to this fast expansion is the German renewable energy act that has motivated households to install PV systems in their houses. This has led to a large amount of producers on the low-voltage network. The small scale producers receive compensation for electricity generated from the PV systems, both when it is used directly in the producer’s home and when it is sold to the grid due to low usage. The systems can be more profitable by storing the energy instead of selling it on the grid. In this way the amount of bought electricity can be reduced. There are concerns regarding the connection of renewable sources to the grid. This project aims to examine the impact from single-phase PV systems on the low-voltage grid. The focus of this bachelor thesis is understanding problems such as harmonic distortion and grid asymmetry. Simulations have been carried out using the software MATLAB in order to study harmonic distortion in the output of a single-phase PV system. Grid asymmetry is examined through calculations and simulations of a worst case scenario in the software NEPLAN. This scenario contains a low voltage grid with a star-star connected transformer, where all PV-systems are connected to the same phase. The simulations in combination with a literature review have provided the conclusion that harmonic distortion caused by the inverter becomes higher when the voltage supply is too low. Integration of battery energy storage systems together with PV systems does not cause additional harmonic distortion. The results also show how single-phase systems contribute to the asymmetry in the grid. When the production from the PV systems is high, and all systems are connected to a certain phase, the current and voltage will also have an impact on the other phases in the worst case scenario.

Η παρούσα διπλωματική εργασία εξετάζει την μελέτη, την εξομοίωση και την κατασκευή μιας νέας τοπολογίας για τη διασύνδεση ενός φωτοβολταϊκού πλαισίου με το δίκτυο χαμηλής τάσης του δικτύου. Η διάταξη που επιλέχτηκε αποτελεί την πρώτη βαθμίδα σε ένα σύστημα που χρησιμοποιεί μετατροπέα δύο βαθμίδων για την αντιστροφή της τάσης του φωτοβολταϊκού πλαισίου έτσι ώστε να επιτευχθεί η σύνδεση του με το δίκτυο. Η βασική λειτουργία της διάταξης αυτής είναι η ανύψωση και η σταθεροποίηση της τάσης στην έξοδο. Το κύκλωμα που μελετήθηκε είναι τύπου Boost με έναν μετασχηματιστή αντί για το πηνίο. Το πρωτεύον του μετασχηματιστή τοποθετείται στη θέση του πηνίου και το δευτερεύον σε σειρά στην έξοδο, έτσι ώστε να επιτυγχάνετε η περαιτέρω ανύψωση της τάσης. Η κατασκευή του μετατροπέα πραγματοποιήθηκε στο εργαστήριο και ο έλεγχος της διάταξης έγινε με τη χρήση μικροελεγκτή (dsPIC30F4011). Τα πειραματικά αποτελέσματα επιβεβαίωσαν την θεωρητική ανάλυση που έγινε και την ορθή λειτουργία του κυκλώματος μας. Ο βαθμός απόδοσης κρίνετε ικανοποιητικά υψηλός καθώς και το κέρδος τάσης του μετατροπέα. Η τοπολογία μπορεί να χρησιμοποιηθεί με διάφορες παραλλαγές της και σε άλλα κυκλώματα επιτρέποντας έτσι την βελτίωση των χαρακτηριστικών τους όπως αύξηση της απόδοσης και του κέρδους τάσης. / -

As more countries progress towards renewable energy, intermittency in the power system is causing an unreliable power supply. Flexibility solutions from prosumers, which both consume and produce electricity, is one solution to provide stability to the power system. Households with both PV and energy storage are studied for this purpose in this thesis where the following flexibility services for both a household and the electricity grid of Sweden are studied: Increasing PV self-consumption, peak shaving, energy arbitrage at the day-ahead electricity market and providing the frequency regulation reserves FCR-N, FCR-D, aFRR and mFRR. Each house is assumed to have a 10 kW PV capacity and a battery capacity of 7.68 kWh. The services are studied in the software HOMER Grid and are modelled in different scales to see how the load in different aggregated levels affect the services. The case studies are a single family house, an overloaded transformer, an energy community and on a national scale. For the aggregated case studies, the potential capacity for PV will be based on the existing Swedish policies and the number of energy storages will be inspired by one the leading countries in Europe in energy storage installations, Germany. The results showed that for a single household the self-consumption and self-sufficiency increased the most with an addition of a battery. The battery was most efficient in peak shaving and reducing the overall electricity cost when the electricity fee targeted both the electricity consumption during peak hours and the monthly peaks. With this price scheme, the payback time of the battery and PV system is around 14 years. However, when the electricity fee is only targeting the electricity consumption during peak hours, the results showed that the monthly electricity demand peaks actually increase with an addition of a battery. For the aggregated case studies, it showed that decentralized batteries are not as effective in decreasing the electricity demand peaks if the peak lasts more than a few hours. On a national scale the results show that 20% of the aggregated batteries capacity is sufficient to provide around 70-100% of each of the frequency reserves individually. The highest savings are gained for the households when both the primary frequency reserves, FCR-N and FCR-D, are provided by the aggregated batteries together with increasing the PV self-consumption, peak shaving and energy arbitrage. The battery payback time is then reduced to 11 years. Based on a sensitivity analysis, the costs that affects the battery payback the most are the investment cost and the power fee. / I takt med att fler länder använder sig mer av förnybar energi, ökar opålitligheten i kraftsystemet på grund av förnybar energis intermittenta natur. Flexibilitetslösningar från konsumenter som kan både producera och konsumera el är en lösning för att förse stabilitet till kraftsystemet. Hushåll med både PV och batteri studeras för detta ändamål i detta examensarbetet där följande flexibilitetstjänster för både hushållet och elnätet studeras: Öka egenkonsumtionen av solel, kapning av effekttoppar, energiarbitrage samt tillhandahålla frekvensregleringens reserver FCR-N, FCR-D, aFRR och mFRR. Varje hus antas ha en 10 kW installerad kapacitet för PV och 7.68 kWh för batteriet. Tjänsterna studeras i programmet HOMER Grid och modelleras i olika skalor för att undersöka hur elkonsumtionen i aggregerade nivåer påverkar dessa tjänster. Fallstudierna är ett enskilt hus, en överbelastad transformator, en samling av hus samt i nationell skala. För de aggregerade fallstudierna kommer den potentiella kapaciteten för PV baseras på Energimyndighetens målbild för produktion av solel och antalet batterier är inspirerade av ett av de ledande länderna i Europa inom energiinstallationer, Tyskland. Resultaten visar att för ett enskilt hushåll ökar egenförbrukningen och självförsörjningen som mest med både batteri och PV. Batteriet var mest effektiv med att minska effekttopparna och den totala elkostnaden när eltariffen innehöll både effekttariffen och tidstariffen. PV systemet med batteriet hade då en återbetalningstid på 14 år. Med endast tidstariffer visar resultatet att de månatliga effekttopparna ökar med tilläggen av batteriet. För de aggregerade fallstudierna visar resultatet att decentraliserade batterier inte är lika effektiva att minska effekttopparna om de varar mer än några timmar. På nationell skala visar resultaten att 20% av den sammanlagda batterikapaciteten är tillräcklig för att förse cirka 70–100% av varje frekvensreserv. Den högsta besparingen för hushållen för den nationella fallstudien fås när både av de primära frekvensreserverna, FCR-N och FCR-D tillhandahålls av de aggregerade batterierna, tillsammans med tjänsterna för att öka PV-konsumtionen, kapning av effekttopparna och energiarbitrage. Batteriets återbetalningstid reduceras då till 11 år. Känslighetsanalysen visar att de kostnader som påverkar batteriets återbetalning mest är investeringskostnaden och effekttariffen.

Esta tese tem como objetivo analisar as políticas públicas de universalização do atendimento de eletricidade, por meio de sistemas fotovoltaicos, em algumas comunidades isoladas e propor procedimentos de aprimoramento. A pesquisa de campo foi baseada em dados qualitativos através de estudo de caso. O trabalho deu-se em três comunidades tradicionais de Ilhabela-SP, onde cem domicílios receberam sistemas capazes de fornecer 30 kWh mensais - SIGFI 30 -, em 2012. cujo financiamento foi pelo Programa Luz para Todos. Foram identificados aspectos facilitadores e barreiras para a adoção dos sistemas fotovoltaicos nessas comunidades. São apresentadas proposições para aprimoramento. O trabalho conclui que nas comunidades de Ilhabela não foi ainda garantida a consecução plena dos objetivos da política pública de poder suprir as necessidades básicas de iluminação, comunicação e refrigeração, notadamente, porque não havia geladeiras; os sistemas fotovoltaicos e a luz elétrica foram muito bem recebidos e foi constatada melhoria da qualidade de vida. / This thesis aims at analyzing public policy of electricity service universalization, by means of photovoltaic systems, in some isolated communities, as well as suggesting improvement procedures. The field research was based on qualitative data collected through case study. The work was performed in three traditional communities in Ilhabela-SP, where a hundred of households received systems capable of supplying monthly 30 kWh SIGFI 30 -, in 2012 which was financed by Light for All Program. Facilitator aspects and barriers for the adoption of the photovoltaic systems in these communities were identified. Suggestions for improvement have been presented. As a result, it is possible to conclude that a plain achievement of the public policy aimed at supplying the basic needs for illumination, communication and refrigeration in those Ilhabela communities, hasnt yet been guaranteed due to the absence of refrigerator. Photovoltaic systems and electricity were well accepted ant it was observed an improvement of quality of life.

Esta tese tem como objetivo analisar as políticas públicas de universalização do atendimento de eletricidade, por meio de sistemas fotovoltaicos, em algumas comunidades isoladas e propor procedimentos de aprimoramento. A pesquisa de campo foi baseada em dados qualitativos através de estudo de caso. O trabalho deu-se em três comunidades tradicionais de Ilhabela-SP, onde cem domicílios receberam sistemas capazes de fornecer 30 kWh mensais - SIGFI 30 -, em 2012. cujo financiamento foi pelo Programa Luz para Todos. Foram identificados aspectos facilitadores e barreiras para a adoção dos sistemas fotovoltaicos nessas comunidades. São apresentadas proposições para aprimoramento. O trabalho conclui que nas comunidades de Ilhabela não foi ainda garantida a consecução plena dos objetivos da política pública de poder suprir as necessidades básicas de iluminação, comunicação e refrigeração, notadamente, porque não havia geladeiras; os sistemas fotovoltaicos e a luz elétrica foram muito bem recebidos e foi constatada melhoria da qualidade de vida. / This thesis aims at analyzing public policy of electricity service universalization, by means of photovoltaic systems, in some isolated communities, as well as suggesting improvement procedures. The field research was based on qualitative data collected through case study. The work was performed in three traditional communities in Ilhabela-SP, where a hundred of households received systems capable of supplying monthly 30 kWh SIGFI 30 -, in 2012 which was financed by Light for All Program. Facilitator aspects and barriers for the adoption of the photovoltaic systems in these communities were identified. Suggestions for improvement have been presented. As a result, it is possible to conclude that a plain achievement of the public policy aimed at supplying the basic needs for illumination, communication and refrigeration in those Ilhabela communities, hasnt yet been guaranteed due to the absence of refrigerator. Photovoltaic systems and electricity were well accepted ant it was observed an improvement of quality of life.

abstract: The students of Arizona State University, under the mentorship of Dr George Karady, have been collaborating with Salt River Project (SRP), a major power utility in the state of Arizona, trying to study and optimize a battery-supported grid-tied rooftop Photovoltaic (PV) system, sold by a commercial vendor. SRP believes this system has the potential to satisfy the needs of its customers, who opt for utilizing solar power to partially satisfy their power needs. An important part of this elaborate project is the development of a new load forecasting algorithm and a better control strategy for the optimized utilization of the storage system. The built-in algorithm of this commercial unit uses simple forecasting and battery control strategies. With the recent improvement in Machine Learning (ML) techniques, development of a more sophisticated model of the problem in hand was possible. This research is aimed at achieving the goal by utilizing the appropriate ML techniques to better model the problem, which will essentially result in a better solution. In this research, a set of six unique features are used to model the load forecasting problem and different ML algorithms are simulated on the developed model. A similar approach is taken to solve the PV prediction problem. Finally, a very effective battery control strategy is built (utilizing the results of the load and PV forecasting), with the aim of ensuring a reduction in the amount of energy consumed from the grid during the “on-peak” hours. Apart from the reduction in the energy consumption, this battery control algorithm decelerates the “cycling aging” or the aging of the battery owing to the charge/dis-charges cycles endured by selectively charging/dis-charging the battery based on need. ii The results of this proposed strategy are verified using a hardware implementation (the PV system was coupled with a custom-built load bank and this setup was used to simulate a house). The results pertaining to the performances of the built-in algorithm and the ML algorithm are compared and the economic analysis is performed. The findings of this research have in the process of being published in a reputed journal. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

This Bachelor’s degree thesis has been performed on behalf of Upplands Lokaltrafik. The thesis aims to suggest a design of a stand-alone renewable power supply system for the bus stops in Uppland. Because of reorganization of Upplands Lokaltrafik and a change in the electricity act they now have to make the decision of either having the future bus stops connected to the electricity grid, with the requirement of installing an electricity meter at each bus stop, or to implement an off grid solution. Upplands Lokaltrafik has a goal of doubling the number of passengers until 2020 and as a part of reaching this goal the bus stops will be designed with electrical features. This thesis also aims to investigate the electricity demand for these future bus stops. The result of the study shows that a connection to the electricity grid and installation of an electricity meter means an investment cost of approximately 83 500 SEK or 123 500 SEK depending on how far cables have to be drawn. The solution with a photovoltaic system with a 180 Wp solar panel would result in an installation cost of 18 500 SEK, which would be both cheaper and more sustainable for the future. However, a photovoltaic system means higher maintenance and a higher risk of destruction. Depending on choice of batteries and the slope of solar panels, both maintenance and risk of vandalization could be diminished.

The ambitious governmental policies, particularly in Europe, in pursuit of established energy targets require an increase in distributed generation. As a result, photovoltaic (PV) technologies have emerged, predominantly at residential Low Voltage (LV) feeders. However, PV rich LV feeders are highly likely to pose technical challenges such as significant voltage rise and thermal overloading. This inevitably limits the volume of PV systems that can be hosted on LV feeders. Therefore, the deployment of solutions that can enable feeders to accommodate greater volumes of PV systems without having any technical issues is crucial. This thesis, consequently, thoroughly investigates one of the potential solutions: transforming the radial operation of LV feeders into ring operation. European-style LV feeders are typically operated in a radial fashion and yet are designed to be reconfigurable with neighbouring feeders. It is, therefore, essential to identify the best pairing option (of PV rich LV feeders) in a practical and straightforward manner due to the large number of existing LV feeders in a given Distribution Network Operator (DNO) area. This thesis proposes a generic innovative methodology to enable DNOs to straightforwardly identify the best pairing feeder; a decision-making tool to facilitate the rapid uptake of PV systems. To accomplish this goal, an impact assessment of a set of real residential LV feeders is carried out to identify the first technical issue/constraint that limits their hosting capacity. Next, regression analyses are carried out to gain an understanding of the relation between this first occurrence of technical issue/constraint and the corresponding level of PV penetration. The most practical and adequately accurate metric needs to be chosen. Feeders are then classified based on the range of metrics to cover all possible pairing cases. Finally, the ring operation of feeders in each class is analysed and hosting capacities are compared to those of radial ones. This process creates a practical matrix from which DNOs can easily identify the best pairing feeders. DNOs are likely to be hesitant to adopt permanent ring operation as it is not typically adopted in traditional LV feeders. Therefore, the switch located between feeders can be operated over time (i.e., dynamic ring operation) to reduce the duration for which ring operation is in place. It is, however, challenging to identify the most favourable control strategy. This thesis proposes different strategies for dynamic ring operation. Note that the most preferable control strategy is that which preserves the benefits of permanent ring operation with the minimum duration of ring operation and minimum number of switching. To achieve this, four different control strategies are explored-using different control cycles and considering hosting capacity, duration and switching. The best control strategy is found to be able to increase hosting capacity as permanent ring operation, reduce switching actions and minimise duration of ring operation compared to other proposed strategies and, crucially, operate ring operation only when it is truly needed. Finally, this thesis investigates the use of ring operation with an LV on-load tap changer (OLTC) as this is recently available voltage control technologies and is increasingly drawing the attention of DNOs. Two approaches are investigated to increase hosting capacity and limit ring operations: the use of the switch and OLTC are controlled separately using local measurements (i.e., localised) and their simultaneous control at the LV transformer level (i.e., centralised). The latter gives the priority to the OLTC to minimise the duration of the ring operation. The assessments are extended to cover an integrated medium and low voltage network to obtain more realistic results. The results show that centralised approach provides better performance considering hosting capacity, the number of switching/tap actions and the duration of ring operation.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / A busca por novos sistemas de refrigeraÃÃo vem se tornando o alvo de estudo de diversos pesquisadores, com o objetivo de diminuir impactos ambientais referentes à destruiÃÃo da camada de ozÃnio e efeito estufa que trazem consigo diversos malefÃcios à vida no planeta. Sistemas de refrigeraÃÃo convencionais respondem por boa parte do consumo de energia elÃtrica de uma residÃncia ou uma empresa (de 20 ou atà 25%), e sÃo normalmente ligados durante o dia , quando a demanda à maior e as tarifas mais caras. Dispositivos de refrigeraÃÃo sÃo indispensÃveis nas atividades humanas, como conservaÃÃo de alimentos, medicamentos, etc. Sistemas fotovoltaicos sÃo fontes de energia elÃtrica confiÃveis e independentes. Por essas razÃes, atualmente, hà um aumento no uso de sistemas de refrigeraÃÃo acionados por energia solar fotovoltaica nas zonas rurais. Tubos de Ranque-Hilsch ou tubos de vÃrtice sÃo geralmente utilizados para refrigeraÃÃo local de baixo custo, onde hà a disponibilidade de ar comprimido. Nesse trabalho, um tubo de vÃrtice foi concebido, testado e otimizado para operaÃÃo em pressÃes inferiores Ãs convencionais, de modo a ser alimentado por um compressor acionado por mÃdulos fotovoltaicos, suprindo as necessidades de esfriamento em localidades desprovidas de energia elÃtrica. Nas mediÃÃes experimentais, foram obtidas temperaturas abaixo do ponto de congelamento da Ãgua por meio da combinaÃÃo de certos parÃmetros, possibilitando a esse sistema de climatizaÃÃo ser utilizado de maneira eficiente e racional em localidades remotas, podendo contribuir para a soluÃÃo da questÃo energÃtica e ambiental da sociedade. / The search for new refrigeration systems has become the target of various researchers. Their goal is to reduce the environment impacts resulting from the destruction of the ozone layer and the greenhouse effects that harm life in the planet Earth. Vapor-compression refrigeration systems represent a big fraction of the world energy consumption in houses and commercial stores (between 20 to 25%) and these systems usually run during the day, when the energy demand and the prices are higher. Refrigeration systems are necessary to todayâs human activities, such as food and medicament conservation, air conditioning, etc. Photovoltaic systems are reliable energy sources and they can operate separately from the distribution energy grid. For these reasons, there is an increase in the use of refrigeration systems powered by solar photovoltaic panels in rural areas. Ranque-Hilsch tubes or vorticity tubes are commonly used for low cost local refrigeration, where compressed air is available. In this study, a vortex tube was designed, tested, and optimized to operate at pressure levels lower than the conventional values. The purpose is to allow its operation by a compressor system powered by solar photovoltaic panels and, therefore, its installation in locations where there is no electrical grid. In the experimental measurements, temperatures below the water freezing point were reached due to the combination of a number of tube parameters. These low temperature values support the use of the vortex tube in air cooling applications in a more efficient and rational energy use, particularly in remote locations, and can contribute to the solution of the energy demand and environmental problems.