Dissertations / Theses on the topic 'Energy curtailment'

The global market for photovoltaics (PV) has increased rapidly: during 2014, 44 times more was installed than in 2004, partly due to a price reduction of 60-70% during the same time period. Economic support schemes that were needed to make PV competitive on the electricity market have gradually decreased and self-consumption of PV electricity is becoming more interesting internationally from an economic perspective. This licentiate thesis investigates self-consumption of residential PV electricity and how more PV power can be allowed in and injected into a distribution grid. A model was developed for PV panels in various orientations and showed a better relative load matching with east-west-oriented compared to south-oriented PV panels. However, the yearly electricity production for the east-west-system decreased, which resulted in less self-consumed electricity. Alternatives for self-consumption of PV electricity and reduced feed-in power in a community of detached houses were investigated. The self-consumption increased more with shared batteries than with individual batteries with identical total storage capacity. A 50% reduction in feed-in power leads to losses below 10% due to PV power curtailment. Methodologies for overvoltage prevention in a distribution grid with a high share of PV power production were developed. Simulations with a case with 42% of the yearly electricity demand from PV showed promising results for preventing overvoltage using centralized battery storage and PV power curtailment. These results show potential for increasing the self-consumption of residential PV electricity with storage and to reduce stress on a distribution grid with storage and power curtailment. Increased self-consumption with storage is however not profitable in Sweden today, and 42% of the electricity from PV is far more than the actual contribution of 0.06% to the total electricity production in Sweden in 2014.

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The current electricity grid suffers from numerous challenges due to the lack of an effective energy management strategy that is able to match the generated power to the load demand. This problem becomes more pronounced with microgrids, where the variability of the load is obvious and the generation is mostly coming from renewables, as it depends on the usage of distributed energy sources. Building a smart microgrid would be much more economically feasible than converting the large electricity grid into a smart grid, as it would require huge investments in replacing legacy equipment with smart equipment. In this paper, application of Internet of Things (IoT) technology in different parts of the microgrid is carried out to achieve an effective IoT architecture in addition to proposing the Internet-of-Asset (IoA) concept that will be able to convert any legacy asset into a smart IoT-ready one. This will allow the effective connection of all assets to a cloud-based IoT. The role of which is to perform computations and big data analysis on the collected data from across the smart microgrid to send effective energy management and control commands to different controllers. Then the IoT cloud will send control actions to solve microgrid's technical issues such as solving energy mismatch problem by setting prediction models, increasing power quality by the effective commitment of DERs and eliminating load shedding by turning off only unnecessary loads so consumers won't suffer from power outages. The benefits of using IoT on various parts within the microgrid are also addressed.

The Swedish island of Gotland , situated about 100 km from mainland Sweden in the Baltic Sea, represents a power system with a high wind power penetration. The island is connected to the mainland Sweden exclusively via two HVDC cables that provide the only source of active power and frequency control. The two cables can operate in different configurations, i.e. import or export power from or to mainland. However, in order to ensure the N-1 criterion, one of the cables currently always must import power from the mainland. This means that the available power exporting capacity is limited to the rated power of one of the cables. Therefore, in the case of having a fault on the exporting HVDC cable during low load demand and high wind power production, the power system will suffer from high active power transients that will increase the frequency above the acceptable threshold. Consequently, the protection system will trip the over-frequency relays, triggering cascading outages on the island that might eventually lead to blackout if the problem is not addressed correctly. Thus, increasing the renewable energy production on Gotland is currently considered as a risk that will increase the probability of instable over-frequency contingencies. This has led the local grid operator to cap the installed wind power capacity to its current level. Therefore, the ability to preserve the stability of the power system during islanded operations until the HVDC cables fault is cleared or the emergency reserves are online is essential for the growth of installed wind power capacity. The main objective of the thesis is to examine the capability of a centralized energy storage along with or without wind curtailment. The ESS is tested for maintaining the frequency stability during the unintentional islanding through dynamic studies using the software PSS/E. The results show that an ESS prevents frequency instabilities and provide frequency response during HVDC cables fault albeit of the absence of any form of rotating inertia. The results show that for today’s 185 MW of installed wind power capacity, an energy storage of 50 MW power capacity will reduce over-frequency instabilities in the case of HVDC cables fault from 13% to 1%. The analysis finds that the power capacity of the energy storage depends on the exported power from the HVDC cables at the instant of fault, which eventually relates to the installed wind power capacity. finally, the study shows that using wind power curtailment will significantly decrease the energy capacity of the energy storage.

The electricity network is undergoing significant changes in the transition to a low carbon system. The growth of renewable distributed generation (DG) creates a number of technical and economic challenges in the electricity network. While the development of the smart grid promises alternative ways to manage network constraints, their impact on the ability of the network to accommodate DG – the ‘hosting capacity’- is not fully understood. It is of significance for both DNOs and DGs developers to quantify the hosting capacity according to given technical or commercial objectives while subject to a set of predefined limits. The combinational nature of the hosting capacity problem, together with the intermittent nature of renewable generation and the complex actions of smart control systems, means evaluation of hosting capacity requires appropriate optimisation techniques. This thesis extends the knowledge of hosting capacity. Three specific but related areas are examined to fill the gaps identified in existing knowledge. New evaluation methods are developed that allow the study of hosting capacity (1) under different curtailment priority rules, (2) with harmonic distortion limits, and (3) alongside energy storage systems. These works together improve DG planning in two directions: demonstrating the benefit provided by a range of smart grid solutions; and evaluating extensive impacts to ensure compliance with all relevant planning standards and grid codes. As an outcome, the methods developed can help both DNOs and DG developers make sound and practical decisions, facilitating the integration of renewable DG in a more cost-effective way.

The increasing share of renewable energy especially wind energy leads to increased share of unpredictable and varying energy into the grid. This leads to congestion in the grid which ultimately results in wind curtailment. In Germany in 2015 alone more than 4000 GWh of wind energy was curtailed. On the other hand, off grid energy requirements for event industry especially concerts and festivals, rely heavily on diesel generators to fulfill their power requirements. This thesis investigates a unique use case for the mobile storage application. The batteries are used to utilize the curtailed wind energy for off-grid applications like festivals and concerts in Germany. The batteries are charged at the wind farm during the duration of curtailment and once they are fully charged, the batteries are transported to the location of concert or an event to provide clean energy. The batteries or storage system used for this case have a capacity of 1.5 MWh and the whole system is constructed in a standard shipping container to allow convenient transportation. According to the findings of this study, the proposed use case can lead to a significant CO2 emission reduction, a single storage system could save up to about 8.4 million kg of CO2, at the events and festivals. Furthermore, it could help in renewable energy integration by providing clean wind energy, that is otherwise curtailed, to festivals and concerts. This study identifies a wind farm with most curtailed energy in Germany with total curtailment duration accounting for about 32% of the time in the year 2017. The technical model, simulated in MATALB/Simulink, successfully charged the battery storage system without any bottleneck. The levelized cost of storage was found to be in comparison with the levelized cost of diesel generators. A single storage system has an ability save up to 8.4 million kg of CO2 emissions. The study further proposes policy suggestions to promote such innovative use case.
Den ökande andelen förnybar energi, särskilt vindenergi, leder en till ökad andel av oförutsägbar intermittent energi till elnätet. Detta leder tidvis till en överbelastning på elnätet, vilket resulterar i att vindkraftverkens elproduktion måste begränsas. Endast i Tyskland under 2015 begränsades 4000 GWh av vindenergi. Samtidigt används diesel generatorer i off-grid områden för att bedriva mässor, marknader, festivaler och liknande arrangemang. Den här rapporten undersöker ett specifikt fall för mobila lagringsmöjligheter. Batterier kan användas för att nyttja den begränsade vindenergin för offgrid evenemang som festivaler och konserter i Tyskland. Batterierna laddas i vindkraftsparker vid hög tillgång till vindenergi och transporteras sedan till ett evenemang för att försörjas med förnybar energi. Batterierna eller lagringsmediet som används för detta fall har en kapacitet på 1,5 MWh och systemet är paketerad i en fraktcontainer för enkel transport. Enligt resultaten från denna studie kan det föreslagna användningsfallet leda till en betydande minskning av koldioxidutsläppen, ett enda lagringssystem skulle kunna spara upp till cirka 8,4 miljoner kg CO2 vid evenemang och festivaler. Dessutom skulle det kunna bidra till integration av förnybar energi genom att tillhandahålla ren vindkraft, som annars begränsas, till festivaler och konserter. Denna studie identifierar en vindkraftspark med den mest begränsade energin i Tyskland med total kapacitetsvaraktighet som står för cirka 32% av tiden under 2017. Den tekniska modellen, simulerad i MATALB / Simulink, laddade batterilagringssystemet framgångsrikt utan flaskhals. De nivåiserade lagringskostnaderna visade sig vara i jämförelse med de nivåiserade kostnaderna för dieselgeneratorer. Ett enda lagringssystem kan spara upp till 8,4 miljoner kg koldioxidutsläpp. Studien föreslår vidare policyförslag för att främja ett sådant innovativt fall.

Transition towards low-carbon energy systems requires an increase in the volume of renewable Distributed Generation (DG), particularly wind and photovoltaic, connected to distribution networks. To facilitate the connection of renewable DG without the need for expensive and time-consuming network reinforcements, distribution networks should move from passive to active methods of operation, whereby technical network constraints are actively managed in real time. This requires the deployment of control solutions that manage network constraints and, crucially, ensure adequate levels of energy curtailment from DG plants by using other controllable elements to solve network issues rather than resorting to generation curtailment only. This thesis proposes a deterministic distribution Network Management System (NMS) to facilitate the connections of renewable DG plants (specifically wind) by actively managing network voltages and congestion in real time through the optimal control of on-load tap changers (OLTCs), DG power factor and, then, generation curtailment as a last resort. The set points for the controllable elements are found using an AC Optimal Power Flow (OPF). The proposed NMS considers the realistic modelling of control by adopting one-minute resolution time-series data. To decrease the volumes of control actions from DG plants and OLTCs, the proposed approach departs from multi-second control cycles to multi-minute control cycles. To achieve this, the decision-making algorithm is further improved into a risk-based one to handle the uncertainties in wind power throughout the multi-minute control cycles. The performance of the deterministic and the risk-based NMS are compared using a 33 kV UK distribution network for different control cycles. The results show that the risk-based approach can effectively manage network constraints better than the deterministic approach, particularly for multi-minute control cycles, reducing also the number of control actions but at the expense of higher levels of curtailment. This thesis also proposes energy storage sizing framework to find the minimum power rating and energy capacity of multiple storage facilities to reduce curtailment from DG plants. A two-stage iterative process is adopted in this framework. The first stage uses a multi-period AC OPF across the studied horizon to obtain initial storage sizes considering hourly wind and load profiles. The second stage adopts a high granularity minute-by-minute control driven by a mono-period bi-level AC OPF to tune the first-stage storage sizes according to the actual curtailment. The application of the proposed planning framework to a 33 kV UK distribution network demonstrates the importance of embedding real-time control aspects into the planning framework so as to accurately size storage facilities. By using reactive power capabilities of storage facilities it is possible to reduce storage sizes. The combined active management of OLTCs and power factor of DG plants resulted in the most significant benefits in terms of the required storage sizes.

This thesis develops methods to increase the amount of renewable energy sources that can be integrated into a power grid. The assessed methods include i) dynamic real-time assessment to enable the grid to be operated closer to its design limits; ii) energy storage and iii) coordinated control of distributed production units. Power grids using such novel techniques are referred to as “Smart Grids”. Under favourable conditions the use of these techniques is an alternative to traditional grid planning like replacement of transformers or construction of a new power line. Distributed Energy Resources like wind and solar power will impact the performance of the grid and this sets a limit to the amount of such renewables that can be integrated. The work develops the hosting capacity concept as an objective metric to quantify the ability of a power grid to integrate new production. Several case studies are presented using actual hourly production and consumption data. It is shown how the different variability of renewables and consumption affect the hosting capacity. The hosting capacity method is extended to the application of storage and curtailment. The goal is to create greater comparability and transparency, thereby improving the factual base of discussions between grid operators, electricity producers and other stakeholders on the amount and type of production that can be connected to a grid.Energy storage allows the consumption and production of electricity to be decoupled. This in turn allows electricity to be produced as the wind blows and the sun shines while consumed when required. Yet storage is expensive and the research defines when storage offers unique benefits not possible to achieve by other means. Focus is on comparison of storage to conventional and novel methods.As the number of distributed energy resources increase, their electronic converters need to provide services that help to keep the grid operating within its design criteria. The use of functionality from IEC Smart Grid standards, mainly IEC 61850, to coordinate the control and operation of these resources is demonstrated in a Research, Development and Demonstration site. The site contains wind, solar power, and battery storage together with the communication and control equipment expected in the future grids.Together storage, new communication schemes and grid control strategies allow for increased amounts of renewables into existing power grids, without unacceptable effects on users and grid performance.
Avhandlingen studerar hur existerande elnät kan ta emot mer produktion från förnyelsebara energikällor som vindkraft och solenergi. En metodik utvecklas för att objektivt kvantifiera mängden ny produktion som kan tas emot av ett nät. I flera fallstudier på verkliga nät utvärderas potentiella vinster med energilager, realtids gränser för nätets överföringsförmåga, och koordinerad kontroll av småskaliga energiresurser. De föreslagna lösningarna för lagring och kommunikation har verifierats experimentellt i en forskning, utveckling och demonstrationsanläggning i Ludvika.
Godkänd; 2014; Bibliografisk uppgift: Nicholas Etherden är industridoktorand på STRI AB i Göteborg. Vid sidan av doktoreringen har Nicholas varit aktiv som konsult inom kraftsystemsautomation och Smarta Elnät. Hans specialitet är IEC 61850 standarden för kommunikation inom elnät, vindkraftparker och distribuerad generering. Författaren har en civilingenjörsexamen i Teknisk fysik från Uppsala Universitet år 2000. Under studietiden läste han även kurser i kemi, miljökunskap och teoretisk filosofi. Han var under studietiden ordförande för Student Pugwash Sweden och ledamot International Network of Engineers and of Scientists for Global Responsibility (INES). Efter studietiden var han ordförande i Svenska Forskare och Ingenjörer mot Kärnvapen (FIMK). Han började sin professionella bana som trainee på ABB i Västerås där han spenderade sex år som utvecklare och grupp ledare för applikationsutvecklingen i ABB reläskydd. I parallell till arbete har han läst elkraft vid Mälardalenshögskola. År 2008 började han på STRI AB som ansvarig för dess IEC 61850 interoperabilitetslab. Han är på uppdrag av Svenska Kraftnät aktiv i ENTSO-E IEC 61850 specificeringsarbete och svensk representant i IEC tekniska kommitté 57, arbetsgrupp 10 som förvaltar IEC 61850 standarden. Han har hållit över 30 kurser i IEC 61850 standarden i fler än 10 länder.; 20140218 (niceth); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Nicholas Etherden Ämne: Elkraftteknik/Electric Power Engineering Avhandling: Increasing the Hosting Capacity of Distributed Energy Resources Using Storage and Communication Opponent: Professor Joao A Peças Lopes, Faculty of Engineering of the University of Porto, Portugal Ordförande: Professor Math Bollen, Avd för energivetenskap, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Måndag den 24 mars 2014, kl 09.00 Plats: Hörsal A, Campus Skellefteå, Luleå tekniska universitet
SmartGrid Energilager

The use of electricity from Distributed Energy Resources like wind and solar powerwill impact the performance of the electricity network and this sets a limit to theamount of such renewables that can be connected. Investment in energy storage andcommunication technologies enables more renewables by operating the networkcloser to its limits. Electricity networks using such novel techniques are referred toas “Smart Grids”. Under favourable conditions the use of these techniques is analternative to traditional network planning like replacement of transformers orconstruction of new power line.The Hosting Capacity is an objective metric to determine the limit of an electricitynetwork to integrate new consumption or production. The goal is to create greatercomparability and transparency, thereby improving the factual base of discussionsbetween network operators and owners of Distributed Energy Resources on thequantity and type of generation that can be connected to a network. This thesisextends the Hosting Capacity method to the application of storage and curtailmentand develops additional metrics such as the Hosting Capacity Coefficient.The research shows how the different intermittency of renewables and consumptionaffect the Hosting Capacity. Several case studies using real production andconsumption measurements are presented. Focus is on how the permitted amountof renewables can be extended by means of storage, curtailment and advanceddistributed protection and control schemes.
Användningen av el från förnyelsebara energikällor som vind och sol kommer att påverka elnätet, som sätter en gräns för hur mycket distribuerad energiproduktion som kan anslutas. Investeringar i storskalig energilager och användning av modern kommunikationsteknologi gör det möjligt att öka andelen förnyelsebarenergi genom att nätet kan drivas närmare sina gränser. Elnät med sådana nya tekniker kallas ofta för ”Smarta Elnät". Implementering av sådana smarta elnät kan vara ett alternativ till traditionell nätplanering och åtgärder som utbyte av transformatorer eller konstruktion av nya kraftledningen.Nätets acceptansgräns är ett objektivt mått för att bestämma gränsen för nätets förmåga att integrera ny förbrukning eller produktion. Målet är att skapa större transparens och bidra till ett bättre faktaunderlag i diskussioner mellan nätoperatörer och ägare av distribuerade energiresurser. Denna avhandling utökar acceptansgränsmetoden för tillämpning med energilager och produktions nedstyrning och utvecklar ytterligare begrepp så som acceptansgränsen koefficienten.Forskningen visar hur varierbarheten hos olika förnyelsebara energikällor samverkar med förbrukningen och påverkar nätets acceptansgräns. Flera fallstudier från verkliga elnät och med uppmätt produktion och konsumtion presenteras. Fokus är på hur den tillåtna mängden förnyelsebara energikällor kan ökas med hjälp av energilagring, kontrollerad produktionsnedstyrning och med avancerad distribuerade skydd och kontroll applikationer.

Godkänd; 2012; Bibliografisk uppgift: Nicholas Etherden works at STRI AB (www.stri.se) in Gothenburg, Sweden. When he is not pursuing his half-time PhD studies he works as a specialist consultant in the field of Power Utility Automation, specialising on the IEC 61850 standard for power utility automation (today widely used in substations as well as some wind parks, hydro plants and DER and Smart Grid applications such as vehicle-to-grid integration). The author of this thesis received his Master of Science in Engineering Physics from Uppsala University 2000. Side tracks during his engineering studies included studies in theoretical philosophy, chemistry, ecology and environmental sciences as well as chairing the Swedish student committee of the Pugwash Conferences on Science and Worlds Affairs and later board member of the International Network of Engineers and of Scientists for Global Responsibility (INES) and chair of Swedish Scientists and Engineers Against Nuclear Arms. He has been a trainee at ABB in Västerås Sweden and spent six years as developer and team leader for the application development of a new relay protection family (ABB IED 670 series). In parallel to his professional work he studied power system engineering at Mälardalens University and travelled to all continents of the world. Since 2008 he is responsible for the STRI IEC 61850 Independent Interoperability Laboratory and a member of IEC Technical Committee 57 working group 10 "Power system communication and associated data models” and UCA/IEC 61850 User group testing subcommittee. He is co-author of IEC 61850-1 and main contributor to “Technical Report on Functional Test of IEC 61850 systems” and has held over 25 hands-on courses around the world on IEC 61850 “Communication networks and systems for power utility automation”.; 20120514 (niceth); LICENTIATSEMINARIUM Ämnesområde: Energiteknik/Energy Engineering Examinator: Professor Math Bollen, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Professor Sami Repo, Tampere University of Technology, Finland Tid: Onsdag den 13 juni 2012 kl 10.00 Plats: Hörsal A, campus Skellefteå, Luleå tekniska universitet

SmartGrid Energilager

Wind power installations have seen a significant rise all over the world in the past decade. Further significant growth is expected in the future. The UK’s ambitions for offshore wind installations are reflected through Round 1, 2 and 3 projects. It is expected that Round 3 alone will add at least 25 GW of offshore wind generation into the system. Current research knowledge is mostly limited to smaller wind farms, the aim of this research is to improve offline and online modelling techniques for large offshore wind farms. A critical part of offline modelling is the design of the wind farm. Design of large wind farms particularly requires careful consideration as high capital costs are involved. This thesis develops a novel methodology which leads to a cost-effective and reliable design of an offshore wind farm. A new industrial-grade software tool is also developed during this research. The tool enables multiple offshore wind farm design options to be built and tested quickly with minimal effort using a Graphical User Interface (GUI). The GUI is designed to facilitate data input and presentation of the results. This thesis also develops an improved method to estimate a wind farm’s energy yield. Countries with large-scale penetration of wind farms often carry out wind energy curtailments. Prior knowledge of estimated energy curtailments from a wind farm can be advantageous to the wind farm owner. An original method to calculate potential wind energy curtailment is proposed. In order to perform wind energy curtailments a network operator needs to decide which turbines to shut down. This thesis develops a novel method to identify turbines inside a wind farm that should be prioritised for shut down and given priority when scheduling preventive maintenance of the wind farm. Once the wind farm has been built and connected to the network, it operates as part of a power system. Real-time online simulation techniques are gaining popularity among system operators. These techniques allow operators to carry out simulations using short-term forecasted wind conditions. A novel method is proposed to probabilistically estimate the power production of a wind farm in real-time, taking into account variation in wind speed and effects of turbulence inside the wind farm. Furthermore, a new probabilistic aggregation technique is proposed to establish a dynamic equivalent model of a wind farm. It determines the equivalent number and parameters of wind turbines that can be used to simulate the dynamic response of the wind farm throughout the year.

Fossil fuel is presently a major source for electricity production, but it contributes significantly to Green House Gas emissions. Wind is a promising alternative, and can potentially become a major power resource in future power systems. Wind power installations are growing significantly for producing clean energy in electric power systems. As the wind penetration continues to increase to relatively high levels, it can significantly affect the overall performance and reliability of the power system. Hence, it becomes very important to accurately model the behaviour of wind, its interaction with conventional sources and also with other wind resources connected to the power system in order to conduct a realistic assessment of system reliability and benefits from wind energy utilization. When the wind penetration levels are low, all the wind energy generated is utilized to serve the load. However, at higher wind penetration levels, wind energy is spilled due to limitations in the operating reserve or ramping capability of the scheduled generating units. The system reliability and the wind energy benefits are reduced as the wind energy spillage increases due to wind curtailment. Hence, accurate wind models should be researched and developed to include wind energy curtailment in the reliability modelling, considering factors such as the system load level, priority loading order of the generating unit and response rates of the generating units. Researchers have not incorporated these factors in wind power modelling and in the adequacy evaluation of wind integrated power systems. A new analytical technique is developed in the subsequent chapters to carry out a comprehensive wind absorption capability evaluation of the power system, and also to incorporate this characteristic in reliability modelling of the system. Wind curtailments can take place not only due to generation constraints, but also due to transmission line constraints depending on the capacity and location of the wind energy resource in the power system, and the power transfer capacity of the transmission lines connected to the wind farm bus. Therefore, reliability modelling of the power system considering wind curtailments due to both generation and transmission constraints should be carried out to assess the impact of wind farms on bulk system reliability and the wind energy benefits. Wind curtailment is incorporated in the composite power system reliability evaluation by modelling the wind resource both as generation and as negative load. The techniques can be utilized to conduct system adequacy and wind energy benefit assessment both at the capacity planning stages and composite generation/transmission planning stages, incorporating wind power curtailment due to generating unit response limitations. As the wind penetration in a power system increases, the wind farms connected to the system are distributed at different geographical locations. Both analytical and Monte Carlo Simulation based techniques have previously been used by the research group at the University of Saskatchewan to include the cross correlation between the wind characteristics of different wind farms in the wind modelling for reliability evaluation of power systems. However, the combined effect of wind diversity and wind curtailments due to both transmission and generation constraints on the system reliability and wind energy benefit assessment has not been considered. The techniques developed for system adequacy and wind energy benefit assessment considering wind curtailment due to generation and transmission constraints are further modified and presented in this thesis to include wind diversity in the analysis. The developed techniques for adequacy evaluation of wind integrated power systems considering wind power curtailment and diversity should be extremely useful for system planning engineers and policy makers as wind power penetration in power systems continues to increase throughout the world.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia
In wind farms, due to the intermittency of the resource and to the fact that most wind parks have an installed power superior to the maximum power injectable into the grid, there is the need of curtailment, leading to resource and economic losses. Allied to these factors, in the future, wind generation should participate in the wholesale electricity market, being crucial the capacity to limit the generation in periods of low market price and to concentrate it in periods of higher price. In order to solve these issues, the use of energy storage systems is essential to store the power that otherwise would be wasted and to obtain a higher income to the wind farm. In this way, there is a need to develop algorithms able to correctly manage the energy storage system and also the wind resource.The main objective of this dissertation was to analyze the impact of an energy storage system, based on batteries, in wind farms. For such purpose, a management system for a wind farm with energy storage was designed. In order to ensure it, two management algorithms developed in MatLab environment were implemented, one with the objective of reducing wind power curtailment and the other, maintaining the curtailment as a priority, but also with the objective of maximizing the economic income of the wind park. The algorithms were tested and simulated for different scenarios and generation profiles and through the developed technical and economic analysis it was possible to verify the system viability. With the developed algorithms it was possible to reduce wind power curtailment and to increase the economic impacts of wind farms.
Nos parques eólicos, devido à intermitência do recurso e ao facto de que, na sua maioria, possuem uma potência instalada superior à máxima potência injetável na rede, surge a necessidade de curtailment, resultando assim em desperdícios de geração e em perdas económicas. Para além de estes fatores, futuramente os parques eólicos serão renumerados em regime de mercado, sendo então crucial limitar a geração em períodos de preço baixo e concentrar a geração em períodos de preço elevado. De forma a resolver estes problemas, o uso de sistemas de armazenamento é essencial, para assim, armazenar a geração, que de outra forma seria desperdiçada e ao mesmo tempo aumentar o lucro do parque. Surge então a necessidade de desenvolver algoritmos capazes de fazerem a gestão correta, não só do sistema de armazenamento, mas também do recurso eólico.O principal objetivo desta dissertação foi analisar o impacto de um sistema de armazenamento de energia elétrica composto por baterias em parques eólicos. Para tal, foi desenvolvido um sistema de gestão de um parque eólico com armazenamento de energia. Com esse intuito, foram desenvolvidos dois algoritmos em ambiente MatLab, um com o objetivo de reduzir curtailment e outro, mantendo a redução do curtailment como prioridade, com o objetivo de maximizar o lucro do parque eólico. Ambos os algoritmos foram simulados e analisados em diferentes cenários e para diferentes níveis de geração, através da análise técnico-económica realizada foi possível verificar a viabilidade do sistema. Com os algoritmos desenvolvidos foi possível reduzir o curtailment assim como aumentar o impacto económico em parques eólicos.

This project examines the challenge of managing the Portugueseelectric powergrid, whichwill experiencethe installationof large amounts of solar and wind capacity and full coalphasing-out during the next decade.The Irena FlexTool is used tostudy the flexibility of the power grid in 2030 under differentscenarios.Weconcludethatthe variable renewable energy (VRE)expectedinstalled capacity will frequentlyproduceexcessiveenergysupply, leading to high levelsof curtailment. Hence, the power baseload price will decreasebetween 1% and 13%andinvestments opportunities between 30,1M and 71,3M (€ 2019)will be generatedby 2030.

De acordo com a Diretiva 2010/31/UE do parlamento europeu e do conselho de 19 de maio de 2010, existe o compromisso dos estados membros para que a partir de 31 de dezembro de 2020 todos os edifícios novos sejam nearly Zero-Energy Buildings (nZEBs). A literatura mostra que a integração de um elevado número de nZEBs em redes de distri-buição de energia elétrica em Baixa Tensão (BT) provoca um excessivo envelhecimento no trans-formador de distribuição originado por fluxos inversos de energia de elevadas amplitudes. Sendo o transformador de distribuição um dos elementos mais importantes e dispendiosos de uma rede de distribuição é importante a criação de soluções que resolvam o problema do seu excessivo envelhecimento. Este estudo contribui com uma solução que utiliza uma estratégia Demand Response (DR) de controlo de termoacumuladores e uma estratégia de curtailment. O caso de estudo incidiu num agregado de 19 edifícios localizados em Évora com perfis de consumo e dados meteorológicos reais. As experiências realizadas estudam o envelhecimento equivalente de um transformador ao longo de um ano de operação, considerando vários cenários. Os resultados demonstram que a combinação das estratégias de curtailment e DR, suportadas pelo controlo de termoacumuladores, permitem reduzir o envelhecimento equivalente do transformador, registado num agregado de nZEBs, em 53% assim como reduzir a emissão de CO2 comparativamente a um cenário onde apenas é aplicado curtailment.

A publicação da Diretiva 2010/31/UE, sobre o desempenho energético dos edifícios, como forma de incentivar um aumento na eficiência energética na União Europeia, teve como consequência um aumento no número de edifícios nZEB – nearly-Zero Energy Building. Este tipo de edifício tem como uma das suas principais características a produção local de energia, através de fontes renováveis, como forma de suprir grande parte das suas necessidades energéticas em determinado intervalo de tempo. Entre as diversas tecnologias para produção local de energia elétrica em nZEBs destaca-se a solar fotovoltaica. Como esta tecnologia tem um perfil de geração muito estrito, dependente do percurso solar ao longo dos dias e meses do ano, quando há excesso de produção e baixa necessidade de consumo, parte da energia gerada é exportada para a rede de distribuição. Esta situação pode causar impactos negativos nos diversos equipamentos da rede de distribuição que alimenta o edifício. Na situação em que o edifício é de maior dimensão, alimentado por um transformador dedicado, a exportação do excedente da produção da fonte local pode ocasionar uma aceleração do processo de envelhecimento deste transformador devido aos fluxos inversos de energia que circulam por ele. Esta dissertação tem como principal objetivo descrever um sistema de proteção (chamado de Sistema Central de Proteção de Transformador – SCPT) para este tipo de transformador. Este sistema terá como princípio de funcionamento o cálculo dos limites técnicos para operação do transformador (em termos da carga máxima permitida para cada condição de temperatura ambiente) e limitar o fluxo inverso no transformador para estes limites. O nível de potência que ultrapassar os limites estabelecidos será tratado através de duas estratégias: armazenamento num banco de baterias e/ou a limitação do fornecimento da matriz fotovoltaica através de curtailment. Este sistema é avaliado em ambiente computacional com dados reais de consumo energético e condições ambientais para a geração de energia recolhidos ao longo do ano de 2013.