Academic literature on the topic 'Dynamic behavior of power grids'

The objective of the research is to develop a cost-effective, dynamic grid controller called the controllable network transformer (CNT) that can be implemented by augmenting existing load tap changing (LTC) transformers with an AC-AC converter. The concept is based on using a fractionally rated direct AC-AC converter to control the power through an existing passive LTC. By using a modulation strategy based on virtual quadrature sources (VQS), it is possible to control both the magnitude and the phase angle of the output voltage of the CNT without having any inter-phase connections. The CNT architecture has many advantages over existing power flow controllers, like absence of low frequency storage, fractional converter rating, retro-fitting existing assets and independent per-phase operation making it potentially attractive for utility applications. The independent control of the magnitude and the phase angle of the output voltage allow independent real and reactive power flow control through the CNT-controlled line. In a meshed network with asymmetric network stresses this functionality can be used to redirect power from critically loaded assets to other relatively under-utilized parallel paths. The power flow controllability of CNT can thus be used to lower the overall cost of generation of power. The solid state switches in the CNT with fast response capability enable incorporation of various additional critical functionalities like grid fault ride through, bypassing internal faults and dynamic damping. This bouquet of features makes the CNT useful under both steady state and transient conditions without compromising the grid reliability.

This thesis presents research results on the effects of tap changing dynamic modeling on power system mid-to-long term voltage behavior. The modeling of tap changing dynamics in voltage stability studies is first addressed. The dynamic operation of an on-load-tap—changing transformer is represented by a highly nonlinear, discrete and time—delay embedded model, which is suitable to mid-to—long term voltage stability studies. Different discrete tap models and their continuous approximations with respect to time and tap position are introduced. The initial emphasis is on studying the influences of different discrete and continuous tap models on voltage stability properties. Combining the tap changer dynamics with the detailed load dynamics, the impacts of different tap models on system voltage behavior are illustrated via theoretical analysis and simulation. It is shown that different stability regions are associated with different continuous tap models and significantly influence the system/voltage behavior, especially under heavily loaded system conditions. The Lyapunov stability method is used to predict the stability region. Limit cycle phenomena are observed in systems with discrete tap models due to the inherent nonlinearities present in these models, the tap dynamics and its interaction with the load dynamics. Conditions for existence of limit cycles are derived via the describing function method. Cases when discrete tap models and their corresponding continuous approximations result in different and / or similar system behavior are also illustrated. Further, a detailed study is given on. the voltage oscillation phenomenon in power systems with on-load—tap—changers. Two kinds of oscillations are considered, namely the well-known voltage oscillations due to tap hunting and oscillations due to tap— load interactions. The focus is on the limit cycle caused by the tap-load interaction. The effects of tap deadband and other parameters such as tap delay time and load recovery time on the existence of system cyclic behavior are carefully investigated. It. is shown that whether or not the limit cycle can be avoided by adjusting the tap deadband depends mainly on the load characteristics. Trajectory sensitivity analysis offers useful information on the influence of parameters on system cyclic behavior. Next, consideration is given to the coordination of a tap changer, as a voltage control device, with other controls, such as a switching capacitor. Using the results of voltage stability analysis as a framework, a new approach for the coordination of dissimilar control actions is derived for arresting voltage collapse. The benefits of coordination of tap locking and capacitor switching are demonstrated foi two possible situations. Firstly, prior capacitor switching at some buses is shown to expand the stability regioh and provide sufficient time for successful tap locking. Secondly, locking taps at some buses can slow the system deterioration and provides time for capacitor switching. The results obtained not only highlight the importance of tap dynamics modeling in voltage behavior studies, but also give an insight into system voltage stability evaluatiofi and control involving on—load-tap—changer dynamics.

Current power systems have remained qualitatively similar to how the were in the last century, especially with respect to the interaction with the end-users. Though present global challenges are putting pressure and questioning their architecture. The increasing demand for electricity - that has become an essential commodity, fundamental for all activities of today's lifestyle - coupled with the concerns about climate change and the need to improve the quality and reliability of the provision urge a modernization of the network. A modernization that needs: to be low carbon, to be reliability and security improving, and to develop new models of customer relationship. Indeed, the thesis deals with important issues that are today in the limelight, such as: i) the importance of the electricity sector in the implementation of climate change mitigation strategies, ii) the innovation of the electricity network as a strategy for reducing emissions, iii) the design of new policies of management of renewable energies and of the new services available, iv) the need to actively involve the users of the network into new styles of consumption / production of energy. All of this is evaluated in a context of evolving energy policies, where the relative long-term importance of the different power generating technologies is changing, especially after the recent events in Japan. The thesis aims at demonstrating the need to promote a qualitative transformation in the system architecture of the “grid” to make it suitable for managing the complexity of the economic scenarios and advanced services that characterize the emerging “knowledge society”, in compliance with the objectives of environmental sustainability and in response to concerns about global climate change. Indeed, because of these concerns and of social and political acceptability issues of nuclear power, as we know it today, the energy scenarios for the next few decades see the emergence of an increasingly important role for renewable energy sources. The general assumption of the thesis is that such a change in the sources of production is likely to cause a major qualitative leap in the power grid. This transformation may induce the evolution of the electricity grid from a classical architecture, top-down and hierarchical, to a more innovative architecture, that will configure the grid (more and more) as a “social ecosystem”, able to include the empowerment of all its stakeholders and to enhance, in particular, the more active role of all users of the new network services. To demonstrate and operationalize the complex nature of this change and the emerging trends, the thesis is organized into three integrated papers that develop and disentangle the system effects of the two technologies that today seem to be at the basis of the possible evolution: Super-Grids and Smart-Grids. The analysis will be conducted using a qualitative-quantitative methodological approach through simulations for both technologies and their integration. The first paper - New electricity generation networks and climate change: the economic potential of national and trans-national super-grids powered by Concentrated Solar Power - develops the analysis of Super-Grids. More in detail, it analyses the system effects and the technological and economic opportunities of transmitting large amounts of electricity over long distances, for the stabilization of anthropogenic emissions of greenhouse gases, with particular attention to the resulting geopolitical dynamics. The analysis is conducted using the simulation platform WITCH, an Integrated Assessment Model (IAM), able to compare this option with other mitigation opportunities, in a framework of intertemporal optimization of resources. In particular, the focus is on the production of electricity from concentrated solar power (CSP) in areas of high solar intensity in places located far from demand centres and, until now, not economically advantageous. The quantitative analysis focuses on the electricity supply made available by the Super-Grid - both domestically and for export/import - evaluating their economic, technological and CO2 mitigation potentials. We have analyzed, in particular, the EU-MENA trade case, though, the results can be expanded qualitatively to consider also the North-South European energy axis, extending the analysis of the geopolitical implications. The second paper - Smart-Grids and Climate Change. Consumer adoption of smart energy behaviour: a system dynamics approach to evaluate the mitigation potential - develops the analysis of Smart-Grids. More in detail, it analyses the system effects of engaging with consumers. More specifically, it looks at the impacts of allowing consumers to: (i) manage more actively and consciously their consumption patterns; (ii) participate to innovative contracting; (iii) generate electricity for own consumption and /or to inject into the grid. Particular interest is directed to the increase in variety of user behaviour (shift, demand response, home automation, generation), caused by the implementation of Smart-Grids, which allows: (i) to form new relationships among actors of the network, (ii) to trigger new processes of “micro production” for energy self-sufficiency to be integrated into the network; and to (iii) improve the management and optimization of the power network. In short, to transform the network into a “sensitive network” capable of opening new organizational spaces/times of action. The analysis is conducted by means of simulations of the adoption dynamics of “smart energy behaviours” by citizens, using the methodology of System Dynamics (J. Forrester) to address the complexity of the dynamics involved. The quantitative analysis focuses on the power supply made available by the change in consumption patterns and by domestic generation, in a “energy self-sufficiency” perspective and on the impacts in terms of demand, system costs and opportunities for mitigation. The qualitative analysis studies the organizational transformations, and the social and cultural evolutions induced by the new interactivity with the end-user The concept of Smart Grid connects the power system to the emerging qualitative transformations and scenarios of the “Knowledge Society” and its newly empowered “Smart Prosumer”. In the third paper - Super & Smart Grid integrated investment scenarios: Green Sustainable Energy Management Strategies & Scenarios - the complex effects of Super and Smart Grid are analysed together. The paper is divided in two parts: the first one where Super and Smart Grids are integrated in one simulation environment to conduct an in-depth economic analysis, and the second part where they are jointly evaluated and compared considering the effects of the innovation of the electricity grid on different levels: environmental, technological, economic, organizational, social and geopolitical, by means of the GEMS (Green Energy Management Strategies foe sustainable scenarios) multi-level evaluation function: GEMS = (Env, Tech, Ec, Org, Soc, GeoP). The proposal is to identify an approach for the analysis and management of the various strategies of green energy generation, that is able to grasp the complexities and interactions of the multiple effects induced by the different options. The quantitative analysis focuses on the integration of the power supply made available jointly by Super and Smart Grids. The qualitative analysis has investigated the new dynamics of empowerment among all the stakeholders involved and the possible impacts on various levels. The synergies of system integration, related to the potential mix of Super and Smart Grids, to manage the evolution of green electricity are also analysed. Concluding, the thesis started with a substantial economic and computational approach, and then was expanded to take into account qualitative aspects that govern the dynamics of the complex “social ecosystem” in play. In synthesis, we analyze the quali-quantitative system effects induced by the impact of the innovation processes in the power network, in an energy market that is not able, alone and in a classical economic perspective, to jointly optimize aspects concerning the environment, technology, organizational structures, economics, society and geopolitics, that are put into play by the introduction of these technological options. These tools are also needed to manage the inevitable conflicts of interest that will arise with the change. We propose an approach “beyond grid parity”, in the sense that we aim at analyzing a broader concept of “costs”, to: (i) identify the paths of evolution of the electrical system in the scenarios of the knowledge society, (ii) the nature and extent of the processes involved, and (iii) to assess the feasibility of accepting the challenge of a low-carbon economy based on renewable energy.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California<br>Data collected during July 1999 at Edwards EAFB by the Advanced Range Telemetry (ARTM) program is examined to characterize the dynamic behavior of multipath interference in an aeronautical telemetry channel. Multipath fade events are analyzed in the frequency domain to show how these fades appear, evolve, and disappear from the channel. A channel model and examples from the channel sounding data are used to show the dynamic nature of these fade events. The Doppler power spectrum is used to quantify the exact time-varying nature of the multipath fade events. The coherence time, or the amount of time the channel can be viewed as unchanging, is obtained from the Doppler power spectrum and is calculated to be 100 ms in the data sets examined in this paper. This implies that adaptive multipath mitigation techniques must have an adaptation bandwidth of 10 Hz.

Ce travail de recherche a été principalement motivé par les avantages importants apportés par la technologie UTBB FDSOI aux applications analogiques et RF de faible puissance. L'objectif principal est d'étudier le comportement dynamique du transistor MOSFET du type UTBB FDSOI et de proposer des modèles prédictifs et des recommandations pour la conception de circuits intégrés RF, en mettant un accent particulier sur le régime d'inversion modérée. Après une brève analyse des progrès réalisés au niveau des architectures du transistor MOSFET, un état de l’art de la modélisation du transistor MOSFET UTBB FDSOI est établi. Les principaux effets physiques impliqués dans le transistor à double grille avec une épaisseur du film de 7 nm sont passés en revue, en particulier l’impact de la grille arrière, à l’aide de mesures et de simulations TCAD. La caractéristique gm/ID en basse fréquence et la caractéristique ym/ID proposée pour la haute fréquence sont étudiées et utilisées dans une conception analogique efficace. Enfin, le modèle NQS haute fréquence proposé reproduit les mesures dans toutes les conditions de polarisation y compris l’inversion modérée jusqu’à 110 GHz<br>This research work has been motivated primarily by the significant advantages brought about by the UTBB FDSOI technology to the Low power Analog and RF applications. The main goal is to study the dynamic behavior of the UTBB FDSOI MOSFET in light of the recent technology advances and to propose predictive models and useful recommendations for RF IC design with particular emphasis on Moderate Inversion regime. After a brief review of progress in MOSFET architectures introduced in the semiconductor industry, a state-of-the-art UTBB FDSOI MOSFET modeling status is compiled. The main physical effects involved in the double gate transistor with a 7 nm thick film are reviewed, particularly the back gate impact, using measurements and TCAD. For better insight into the Weak Inversion and Moderate Inversion operations, both the low frequency gm/ID FoM and the proposed high frequency ym/ID FoM are studied and also used in an efficient first-cut analog design. Finally, a high frequency NQS model is developed and compared to DC and S-parameters measurements. The results show excellent agreement across all modes of operation including very low bias conditions and up to 110 GHz

L’objectif de ce travail de recherche est de concevoir un amplificateur de puissance sur la base de considérations électrothermiques. Il décrit la question du dynamique EVM et du « paquet long » lors de la conception de l’amplificateur avec des transistors bipolaires à hétérojonctions. Basé sur le comportement électrothermique du circuit, une méthode d’optimisation de l’EVM statique et dynamique est proposée. Un frontend RF complet (amplificateur de puissance + coupleur + interrupteur + amplificateur faible bruit) est conçu pour le dernier standard WLAN : le Wi-Fi 6. La distribution de temperature dynamique dans le circuit est analysée. Son effet sur les performances de la puce est quantifié. Enfin, une polarisation adaptative programmable a été conçue pour garder des performances optimales sur toute la plage de température. Les mesures du circuit montre tout l’effet bénéfique de cette compensation, permettant de garder le dynamique EVM en dessous de -47 dB sur la plage de température ambiante de -40 à 85°C<br>The aim of this work is to design a power amplifier based on electrothermal considerations. It describes the Dynamic Error Vector Magnitude challenge and long packet issue when designing a power amplifier with hetero-junction bipolar transistors. Based on the circuit electrothermal behavior, an optimization method of both the static and dynamic linearity is proposed. A complete RF front-end (PA + coupler + switch + LNA) is designed for the latest WLAN standard: the Wi-Fi 6. The dynamic temperature distribution in the circuit is analyzed. It’s impact on the performances is quantified. Finally, a programmable temperature dependent bias is designed to compensate for performance degradation. The measurements show a significant linearity improvement with this compensation, allowing the PA to maintain the DEVM lower than -47dB at 14.5 dBm output power, over a large ambient temperature range from -40°C to 85°C

Rising concerns related to the effects of traffic congestion have led to the search for alternative transportation solutions. Advances in battery technology have resulted in an increase of electric vehicles (EVs), which serve to reduce the impact of many of the negative consequences of congestion, including pollution and the cost of wasted fuel. Furthermore, the energy-efficiency and quiet operation of electric motors have made feasible concepts such as Urban Air Mobility (UAM), in which electric aircraft transport passengers in dense urban areas prone to severe traffic slowdowns. Electrified transportation may be the solution needed to combat urban gridlock, but many logistical questions related to the design and operation of the resultant transportation networks remain to be answered. This research begins by examining the near-term effects of EV charging networks. Stationary plug-in methods have been the traditional approach to recharge electric ground vehicles; however, dynamic charging technologies that can charge vehicles while they are in motion have recently been introduced that have the potential to eliminate the inconvenience of long charging wait times and the high cost of large batteries. Using an agent-based model verified with traffic data, different network designs incorporating these dynamic chargers are evaluated based on the predicted benefit to EV drivers. A genetic optimization is designed to optimally locate the chargers. Heavily-used highways are found to be much more effective than arterial roads as locations for these chargers, even when installation cost is taken into consideration. This work also explores the potential long-term effects of electrified transportation on urban congestion by examining the implementation of a UAM system. Interdependencies between potential electric air vehicle ranges and speeds are explored in conjunction with desired network structure and size in three different regions of the United States. A method is developed to take all these considerations into account, thus allowing for the creation of a network optimized for UAM operations when vehicle or topological constraints are present. Because the optimization problem is NP-hard, five heuristic algorithms are developed to find potential solutions with acceptable computation times, and are found to be within 10% of the optimal value for the test cases explored. The results from this exploration are used in a second agent-based transportation model that analyzes operational parameters associated with UAM networks, such as service strategy and dispatch frequency, in addition to the considerations associated with network design. General trends between the effectiveness of UAM networks and the various factors explored are identified and presented.

Des solutions innovantes doivent être développées pour envisager l'avenir des systèmes électriques face à un nombre grandissant de contraintes. En particulier, le stockage d'énergie est pressenti comme un soutien indispensable à l'essor massif dans les réseaux de distribution de sources de production exploitant les énergies renouvelables. Les présents travaux visent à apporter des éléments de réflexion sur cette option technique qui arrive à maturité et suscite l'intérêt. Dans un premier temps, des méthodes d'étude sont proposées pour cerner le potentiel et les opportunités du stockage distribué. Une grille de caractérisation des technologies est introduite et sa mise en œuvre souligne des performances intéressantes à des coûts qui, cependant, demeurent élevés. Pour rendre leur utilisation réaliste, la valeur de ces dispositifs pour les systèmes électriques est donc critique. Nous l'analysons en deux étapes : une classification de leurs services pour les différents acteurs en présence est définie avant d'aborder la mutualisation de fonctions, requise pour favoriser l'atteinte d'une rentabilité, via une approche originale. Cette démarche aboutit à l'identification de configurations porteuses qui méritent des études plus poussées. Pour ce faire, un modèle général de comportement des unités de stockage est développé dans un second temps. Interfacé à un logiciel de simulation dynamique des réseaux, il permet d'évaluer l'utilisation de telles installations pour diverses offres de services. Ces outils sont appliqués et validés expérimentalement sur la caractérisation d'une réserve impulsionnelle fournie par le stockage pour réduire les délestages dans les systèmes insulaires