2,204 research outputs found

    Modelling of 3-Phase p-q Theory-Based Dynamic Load for Real-Time Simulation

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    This article proposes a new method of modelling dynamic loads based on instantaneous p-q theory, to be employed in large powers system network simulations in a digital real-time environment. Due to the use of computationally heavy blocks such as phase-locked-loop (PLL), mean calculation,and coordinate transformation blocks (e.g., abc–dq0), real-time simulation of large networks with dynamic loads can be challenging. In order to decrease the computational burden associated to the dynamic load modelling, a p-q theory-based approach for load modelling is proposed in this paper. This approach is based on the well-known p-q instantaneous theory developed for power electronics converters, and it consists only of linear controllers and of a minimal usage of control loops, reducing the required computational power. This improves real-time performance and allows larger scale simulations. The introduced p-q theory-based load (PQL) model has been tested on standard networks implemented in a digital real time simulator, such as the SimBench semi-urban medium voltage network and the 118-bus Distribution System, showing significant improvement in terms of computational capability with respect to standard load models (e.g., MATLAB/Simulink dynamic load)

    1. Helgoland Power and Energy Conference - 24. Dresdener Kreis 2023

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    Der Sammelband "1. Helgoland Power and Energy Conference" beinhaltet neben einem kurzen Bericht zum 24. Treffen des Dresdener Kreises 2023 wissenschaftliche Beiträge von Doktoranden der beteiligten Hochschulinstitute zum Thema Elektroenergieversorgung. Der Dresdener Kreis setzt sich aus der Professur für Elektroenergieversorgung der Technischen Universität Dresden, dem Fachgebiet Elektrische Anlagen und Netze der Universität Duisburg-Essen, dem Fachgebiet Elektrische Energieversorgung der Leibniz Universität Hannover und dem Lehrstuhl Elektrische Netze und Erneuerbare Energie der Otto-von-Guericke Universität Magdeburg zusammen und trifft sich einmal im Jahr zum fachlichen Austausch an einer der beteiligten Universitäten

    Indie encounters: exploring indie music socialising in China

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    Indie music, a genre deeply rooted in rock and punk music, is renowned for its independence from major commercial record labels. It has emerged as a choice for music consumers seeking alternatives to mainstream popular music, catering to a niche music preference. The minority nature of indie music not only provides its lovers with a profound space for individual expression and a sense of collective belonging but also introduces other challenges into their social lives. Recently, the field of music sociology has proposed a more diverse perspective to observe and analyse the intricate role of music for individuals and society. In this context, regarding Chinese indie music lovers with niche music preferences, how their indie music practices integrate into their social lives and how they navigate their niche music tastes have become worthwhile topics of exploration. Drawing on interviews with 31 Chinese indie music lovers and extensive online ethnography, this thesis investigates how Chinese indie music lovers comprehend and engage with indie music, and how the power of indie music shapes them and their social behaviours. I employ the theoretical framework of ‘music in action’ (Hennion, 2001; DeNora, 2011, 2016) and symbolic interactionism (Mead, 1934; Goffman, 1959; Blumer, 1969) to examine the dynamic and multifaceted roles of indie music in the social lives of Chinese indie music lovers. I develop a concept of ‘music socialising’ to delve into several key aspects of music lovers’ social practices. I contend that through various forms of musical activities such as music selection, live music attendance, and digital practices, indie music lovers exhibit strategic and reflexive characteristics in their music practices. These practices actively contribute to constructing and maintaining self and identity, negotiating social ties, and forming and mediating collectivity within a broader social landscape. It is through these processes that the music practices of Chinese indie music lovers are endowed with meanings, thereby shaping their social reality. This thesis presents a rich and nuanced picture of the social experiences of Chinese indie music lovers, uncovering the transformative power of their indie music practices. It presents a compelling argument for the significance of music as a social agency, highlighting the complex interactions between music, individuals, and society. By bridging theoretical insights with rich empirical data, this thesis contributes to our understanding of the socio-cultural dimensions of music, offering fresh perspectives on the role of indie music in contemporary Chinese society

    Evaluación probabilística y armónica de parámetros de calidad de energía de recursos energéticos distribuidos en una red de distribución

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    Distributed energy resources (DERs) are leading actors in energy transition worldwide. Despite the environmental benefits, DERs are intermittent (consumption/generation power changes according to the input variables), and the use of power electronic devices affects the power quality in distribution networks. Typically, models and simulations (deterministic or probabilistic) are proposed to estimate such impacts. However, previous studies have analyzed the main effects caused by one or two DERs during a day. These studies had a reduced level of detail in the applied methodology in modeling and impact evaluation, or they did not consider that the harmonic distortion level depends on input variables. The aim of this article was to develop a probabilistic harmonic simulation approach to characterize the hourly effect of photovoltaic systems (PVS), battery energy storage systems, and electric vehicle charging stations in a 34-node IEEE test feeder. The individual and collective effect estimation of the DERs consists of the hourly quantification of the effective voltage value, voltage unbalance, power factor, and harmonic distortion, with data obtained using Python and PowerFactory co-simulation for 23 operation scenarios. These impacts were assessed through indicators proposed in the literature and hypothesis tests (inferential statistics). Each DER generally operates at a specific time, making it easy to identify the individual effects of network parameters. The PVS increased the effective voltage value and total harmonic distortion. However, electric vehicles and batteries increase the voltage unbalance and power factor due to the two-phase connection in some network nodes.Los recursos energéticos distribuidos (RED) son actores líderes en la transición energética en todo el mundo. A pesar de los beneficios ambientales, los RED son intermitentes (la energía de consumo/generación cambia según las variables de entrada), y el uso de dispositivos de electrónica de potencia afecta la calidad de la energía en las redes de distribución. Por lo general, se proponen modelos y simulaciones (deterministas o probabilísticas) para estimar dichos impactos. Sin embargo, estudios previos han analizado los principales efectos causados por uno o dos RED durante un día, con un nivel de detalle reducido en la metodología aplicada en el modelado y evaluación de impacto, o sin considerar que el nivel de distorsión armónica depende de las variables de entrada. El objetivo del presente artículo fue desarrollar un enfoque de simulación armónica probabilística para caracterizar el efecto horario de los sistemas fotovoltaicos (SFV), los sistemas de almacenamiento de energía de baterías y las estaciones de carga de vehículos eléctricos en un alimentador de prueba IEEE de 34 nodos. La estimación del efecto individual y colectivo del RED consistió en la cuantificación horaria del valor efectivo de tensión, desequilibrio de tensión, factor de potencia y distorsión armónica, con datos obtenidos mediante co-simulación Python y PowerFactory para 23 escenarios de operación. Estos impactos fueron evaluados a través de indicadores propuestos en la literatura y pruebas de hipótesis (estadística inferencial). Cada RED generalmente opera en un momento específico, lo que facilita la identificación de los efectos individuales de los parámetros de la red. El SFV aumentó el valor de voltaje efectivo y la distorsión armónica total. Sin embargo, los vehículos eléctricos y las baterías aumentan el desequilibrio de tensión y el factor de potencia debido a la conexión bifásica en algunos nodos de la red

    Optimising heating and cooling of smart buildings

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    This thesis is concerned with optimization techniques to improve the efficiency of heating and cooling of both existing and new buildings. We focus on the thermal demand-side and we make novel contributions to the optimality of both design and operational questions. We demonstrate that our four novel contributions can reduce operations cost and consumption, optimize retrofit and estimate relevant parameters of the built environment. The ultimate objective of this work is to provide affordable and cost-effective solutions that take advantage of local existing resources. This work addresses four gaps in the state-of-the-art. First, we contribute to current building practice that is mostly based on human experience and simulations, which often leads to oversized heating systems and low efficiency. The results in this thesis show the advantages of using optimization approaches for thermal aspects in buildings. We propose models that seek optimal decisions for one specific design day, as well as an approach that optimizes multiple day-scenarios to more accurately represent a whole year. Second, we study the full potential of buildings’ thermal mass and design. This has not been fully explored due to two factors: the complexity of the mathematics involved, and the fast developing and variety of emerging technologies and approaches. We tackle the mathematical challenge by solving non-linear non-convex models with integer decisions and by estimating building’s thermal mass. We support rapid architectural development by studying flexible models able to adapt to the latest building technologies such as passive house design, smart façades, and dynamic shadings. Third, we consider flexibility provision to significantly reduce total energy costs. Flexibility studies often only focus on flexible building loads but do not consider heating, which is often the largest load of a building and is less flexible. Because of that, we study and model a building’s heating demand and we propose optimization techniques to support greater flexibility of heating loads, allowing buildings to participate more efficiently in providing demand response. Fourth, we consider a building as an integrated system, unlike many other modelling approaches that focus on single aspects. We model a building as a complex system comprising the building’s structure, weather conditions and users’ requirements. Furthermore, we account for design decisions and for new and emerging technologies, such as heat pumps and thermal storage. Optimal decisions come from the joint analysis of all these interconnected factors. The thesis is structured in three parts: the introduction, the main body and the conclusions. The main body is made by five chapters, each of which focuses on one research project and has the following structure: overview, introduction, literature review, mathematical framework description, application and results section, conclusion and future works. The first two chapters discuss the optimization of operational aspects. The first focuses on a single thermal zone and the second in two connected ones. The third chapter is a continuation of the first two, and presents an approach to optimize both operations and design of buildings in a heat community. This approach integrates the use of an energy software already in the market. The fourth chapter discusses an approach to find the optimal refurbishment of an existing building at minimum cost. The fifth chapter shows an inferring model to represent a house of a building stock. We study the common case where the house’s data is lacking or inaccurate, and we present a model that is able to estimate the required thermal parameters for modelling the house using only heating demand

    Price formation in Local Electricity Markets

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    Autonomous Demand Side Management of Electric Vehicles

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    There is an error in the table of content, where publication A and B have swiched places.Demand-side management approaches that exploit the temporal flexibility of electric vehicles have attracted much attention in recent years due to the increasing market penetration. These demand-side management measures contribute to alleviating the burden on the power system, especially in distribution grids where bottlenecks are more prevalent. Electric vehicles can be defined as an attractive asset for distribution system operators, which have the potential to provide grid services if properly managed. In this thesis, first, a systematic investigation is conducted for two typically employed demand-side management methods reported in the literature: A voltage droop control-based approach and a market-driven approach. Then a control scheme of decentralized autonomous demand side management for electric vehicle charging scheduling which relies on a unidirectionally communicated grid-induced signal is proposed. In all the topics considered, the implications on the distribution grid operation are evaluated using a set of time series load flow simulations performed for representative Austrian distribution grids. Droop control mechanisms are discussed for electric vehicle charging control which requires no communication. The method provides an economically viable solution at all penetrations if electric vehicles charge at low nominal power rates. However, with the current market trends in residential charging equipment especially in the European context where most of the charging equipment is designed for 11 kW charging, the technical feasibility of the method, in the long run, is debatable. As electricity demand strongly correlates with energy prices, a linear optimization algorithm is proposed to minimize charging costs, which uses next-day market prices as the grid-induced incentive function under the assumption of perfect user predictions. The constraints on the state of charge guarantee the energy required for driving is delivered without failure. An average energy cost saving of 30% is realized at all penetrations. Nevertheless, the avalanche effect due to simultaneous charging during low price periods introduces new power peaks exceeding those of uncontrolled charging. This obstructs the grid-friendly integration of electric vehicles.publishedVersio

    Transforming AC-Powered Production Machines For Operation In DC Microgrids: From Methodology To Realization

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    Abstract: Manufacturing processes play a major role in the emission of greenhouse gases. To achieve the international goal of climate neutrality, it is a must to decrease the amount of energy consumed by factories and their production machines. A promising approach is to improve grid efficiency and reduce voltage converter losses by using DC microgrids (DC-MGs). Furthermore, DC-MGs have proven suitable for an efficient integration of renewable energy producers and prosumers with energy recuperation capabilities. To establish DC-MGs successfully in production environments, it is necessary to provide solutions for DC-MG integration of AC-powered machines. This paper describes how to enable production machines originally designed for AC-grid use to be operated on industrial DC-MGs. The article focuses on a methodology for AC-DC transformation of machines, including definition of specifications, system analysis, and redesign. The methodology is described using the example of an injection-moulding machine. Finally, the results of the transformation process are evaluated
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