Modeling And Control Of Power Converters In Weak And Unbalanced Electric Grids

Grid converters increasingly affect power system operation due to the increasing share of renewable energy sources and less conventional power plants. This shift in power generation leads to converter-dominated weak grids, which show critical stability phenomena but also enable converters to contribute to grid stability and voltage support. This thesis presents critical parts of converter controls and describes models to assess their characteristics. These models are used to derive design criteria and dedicated stability analysis methods for grid converter controls. Der steigende Anteil an erneuerbaren Energien in den Energieversorgungsnetzen führt zur Verdrängung konventioneller Kraftwerke. Diese Entwicklung lässt umrichterdominierte und schwache Netzabschnitte entstehen, die kritischen Stabilitätsmechanismen unterliegen, allerdings auch ermöglichen, dass Umrichter aktiv zur Netzstützung und Netzstabilität beitragen können. Die vorliegende Arbeit beschreibt kritische Regelungskomponenten der Umrichter und deren Modellierung. Auf Basis der Modelle werden Auslegungskriterien für die Regelungen abgeleitet und dedizierte Stabilitätsanalysemethoden präsentiert.

Modern power electronic converters are involved in a very broad spectrum of applications: switched-mode power supplies, electrical-machine-motion-control, active power filters, distributed power generation, flexible AC transmission systems, renewable energy conversion systems and vehicular technology, among them. Power Electronics Converters Modeling and Control teaches the reader how to analyze and model the behavior of converters and so to improve their design and control. Dealing with a set of confirmed algorithms specifically developed for use with power converters, this text is in two parts: models and control methods. The first is a detailed exposition of the most usual power converter models: · switched and averaged models; · small/large-signal models; and · time/frequency models. The second focuses on three groups of control methods: · linear control approaches normally associated with power converters; · resonant controllers because of their significance in grid-connected applications; and · nonlinear control methods including feedback linearization, stabilizing, passivity-based, and variable-structure control. Extensive case-study illustration and end-of-chapter exercises reinforce the study material. Power Electronics Converters Modeling and Control addresses the needs of graduate students interested in power electronics, providing a balanced understanding of theoretical ideas coupled with pragmatic tools based on control engineering practice in the field. Academics teaching power electronics will find this an attractive course text and the practical points make the book useful for self tuition by engineers and other practitioners wishing to bring their knowledge up to date.

This book covers advancements of power electronic converters and their control techniques for grid integration of large-scale renewable energy sources and electrical vehicles. Major emphasis are on transformer-less direct grid integration, bidirectional power transfer, compensation of grid power quality issues, DC system protection and grounding, interaction in mixed AC/DC system, AC and DC system stability, magnetic design for high-frequency high power density systems with advanced soft magnetic materials, modelling and simulation of mixed AC/DC system, switching strategies for enhanced efficiency, and protection and reliability for sustainable grid integration. This book is an invaluable resource for professionals active in the field of renewable energy and power conversion.

Grid Connected Converters: Modeling, Stability and Control discusses the foundations and core applications of this diverse field, from structure, modeling and dynamic equivalencing through power and microgrids dynamics and stability, before moving on to controller synthesis methodologies for a powerful range of applications. The work opens with physical constraints and engineering aspects of advanced control schemes. Robust and adaptive control strategies are evaluated using real-time simulation and experimental studies. Once foundations have been established, the work goes on to address new technical challenges such as virtual synchronous generators and synergic inertia emulation in response to low inertia challenges in modern power grids.The book also addresses advanced systematic control synthesis methodologies to enhance system stability and dynamic performance in the presence of uncertainties, practical constraints and cyberattacks. Addresses new approaches for modeling, stability analysis and control design of GCCs Proposes robust and flexible GCC control frameworks for supporting grid regulation Emphasizes the application of GCCs in inertia emulation, oscillation damping control, and dynamic shaping Addresses systematic control synthesis methodologies for system security and dynamic performance

Presents Fundamentals of Modeling, Analysis, and Control of Electric Power Converters for Power System Applications Electronic (static) power conversion has gained widespread acceptance in power systems applications; electronic power converters are increasingly employed for power conversion and conditioning, compensation, and active filtering. This book presents the fundamentals for analysis and control of a specific class of high-power electronic converters—the three-phase voltage-sourced converter (VSC). Voltage-Sourced Converters in Power Systems provides a necessary and unprecedented link between the principles of operation and the applications of voltage-sourced converters. The book: Describes various functions that the VSC can perform in electric power systems Covers a wide range of applications of the VSC in electric power systems—including wind power conversion systems Adopts a systematic approach to the modeling and control design problems Illustrates the control design procedures and expected performance based on a comprehensive set of examples and digital computer time-domain simulation studies This comprehensive text presents effective techniques for mathematical modeling and control design, and helps readers understand the procedures and analysis steps. Detailed simulation case studies are included to highlight the salient points and verify the designs. Voltage-Sourced Converters in Power Systems is an ideal reference for senior undergraduate and graduate students in power engineering programs, practicing engineers who deal with grid integration and operation of distributed energy resource units, design engineers, and researchers in the area of electric power generation, transmission, distribution, and utilization.

Lithium plating is not only the most severe ageing mechanism in lithium-ion batteries (LIBs) but also becoming more and more important due the increasing presence of electric vehicles (EVs). In EVs the extreme conditions causing lithium plating, like very high charging currents and low environment temperatures, are much more prevalent than in consumer electronics. Due to the high number of factors that influence the plating process, ranging from the cell geometry to the chemical composition of the electrolyte, a deeper understanding of the plating process is still lacking. Without this knowledge it is hard to design cells in a plating resistant way, or to operate cells under the ideal conditions to minimize plating. This thesis aims at showing different methods to investigate the plating process on three different levels. The first method is on the cell level, investigating the behaviour of the whole cell during plating. It contains the analysis of the voltage and current profiles that show an atypical behaviour during plating. The focus of the analysis is on the current profile of the constant voltage (CV) phase during charging under low temperature conditions leading to plating. This current profile can be fitted with the Johnson-Mehl-Avrami-Kolmogorov (JMAK) function that describes the electrochemical deposition process of a metallic species on a surface. The resulting fitting parameters can be utilized to characterize the plating behaviour of the cell as well as better estimate the amount of plated lithium than commonly used methods. It can also potentially predict the future safety risk due to dendrite formation. In the second part the chemical composition of the surface electrolyte interface (SEI) is investigated using X-ray photoelectron spectroscopy (XPS). The composition as well as the mechanical properties of the SEI are strongly influencing the plating process and preliminary work has shown that plating is also changing the morphology of the SEI and increasing its thickness drastically. Cells under different conditions (plated, charged and discharged) as well as cells of different manufacturers have been probed using XPS. During the measurements an unwanted side effect of the experimental setup was discovered that lead to a migration of lithium to the surface of the sample and was distorting the measurement results. Regardless of the effect, it was possible to see that the SEI can have a very different composition in cells of different manufacturers and that plating not only changes the morphology but also the composition of the SEI. The unwanted side effect could furthermore be utilized to identify samples that were plated recently and could be used in further more controlled experiments to localize lithium depositions on plated samples. In the last part the particle structure of the anode surface of cells of different manufacturers was investigated using a watershed particle detection algorithm on laser scanning microscopy (LSM) images of the anode surfaces. The distributions of the particle sizes have then been compared to the capacity loss in plated cells. It was shown that the capacity loss correlates with parameters extracted from the particle size distributions. It is however necessary to create more data to verify this correlation. In summary this thesis utilized new methods to detect or characterize plating on different levels of magnification, from the cell level to the chemical composition. New approaches were found to predict a cells future plating behaviour, spatially localize plated areas on the anode and design cells in a plating resistant way. Lithium Plating ist nicht nur der Alterungsmechanismus in Lithium-Ionen-Batterien mit dem größten Kapazitätsverlust, sondern wird auch im Zuge der voranschreitenden Elektrifizierung des Personenverkehrs immer wichtiger. In Elektrofahrzeugen finden sich die extremen Zustände, wie niedrige Ladetemperaturen und hohe Ladestrome, unter denen Plating auftritt, deutlich häufiger als in Unterhaltungstechnik. Durch die Vielzahl von Parametern, von der Zellgeometrie bis hin zur Elektrolyzusammensetzung, die Plating beeinflussen, fehlt immer noch ein tieferes Verständnis des Plating-Prozesses. Ohne dieses Wissen ist es schwer, Zellen zu designen, die resistent gegen Plating sind oder Zellen unter optimalen Bedingungen zu betreiben um Plating zu minimieren. Das Ziel dieser Arbeit ist es, verschiedene Methoden aufzuzeigen, die die Untersuchung von Plating auf drei verschiedenen Ebenen ermöglichen. Die erste Methode untersucht das Gesamtverhalten der Zelle auf Zellebene. Hierbei wird das atypische Verhalten der Strom- und Spannunsprofile wahrend des Plating-Vorgangs analysiert. Der Fokus liegt dabei auf der Untersuchung der Konstantstrom-Phase bei niedrigen Temperaturen während der Ladung. Das Stromprofil dieser Phase kann mit der JMAK-Funktion gefittet werden, welche die elektrochemische Abscheidung eines Metalls auf einer Oberfläche beschreibt. Die resultierenden Fitting-Parameter können genutzt werden, um das Plating-Verhalten vorherzusagen und sind gleichzeitig eine bessere Abschätzung fur die Menge an geplatetem Lithium im Vergleich zu gängigen Methoden. Die Ergebnisse konnten außerdem helfen das Sicherheitsrisiko der Zelle bei Dendritenbildung vorherzusagen. Im zweiten Teil wird die chemische Zusammensetzung der SEI mittels XPS untersucht. Die Zusammensetzung, wie auch die mechanischen Eigenschaften der SEI, beeinflussen den Plating-Prozess stark und es wurde in vorhergehenden Arbeiten gezeigt, dass Plating auch die Morphologie und Dicke der SEI drastisch verändern kann. Zellen in verschiedenen Zuständen (geplatet, geladen, entladen), sowie Zellen verschiedener Hersteller wurden mit XPS untersucht. Während der Messungen wurde ein ungewollter Nebeneffekt des Messaufbaus entdeckt, der zu einer Migration von Lithium an die Oberflache der Proben geführt und die Messergebnisse verfälscht hat. Unabhängig von diesem Effekt war es dennoch möglich, zu zeigen, dass die SEI in Zellen verschiedener Hersteller stark unterschiedliche Zusammensetzungen haben kann und dass Plating nicht nur die Morphologie der SEI beeinflusst, sondern auch die chemische Zusammensetzung. Weiterhin konnte der ungewollte Nebeneffekt verwendet werden, um Proben zu identifizieren, die vor kurzem geplatet wurden und konnte in zukünftigen Arbeiten verwendet werden, um lokalisiert Lithium-Ablagerungen auf geplateten Proben zu identifizieren. Im letzten Teil wurde die Partikelstruktur der Anoden von Zellen verschiedener Zellhersteller mit Hilfe einer watershed-Partikeldetektion an LSM-Bildern untersucht. Die Verteilung der Partikelgrößen wurde mit dem Kapazitätsverlust gleicher Zelle durch Plating verglichen. Es wurde gezeigt, dass der Kapazitätsverlust mit Parametern, die aus den Partikelverteilungen extrahiert wurden, korreliert. Ein größerer Datensatz ist jedoch notwendig, um diese Ergebnisse zu validieren. Zusammenfassend hat diese Arbeit verschiedene neue Methoden aufgezeigt, um Plating auf verschiedenen Vergrößerungsebenen zu detektieren und zu charakterisieren. Neue Ansätze wurden gefunden, um das Platingverhalten von Zellen vorherzusagen, lokalisiertes Lithium auf der Oberfläche zu detektieren und Zellen platingresistenter designen zu können.

This book covers the fundamentals of power electronic converter modeling and control, digital simulation, and experimental studies in the area of renewable energy systems and AC/DC microgrid. Recent advanced control methods for voltage source inverters (VSIs) and the hierarchical controlled islanded microgrid are discussed, including the mathematical modeling, controller synthesis, parameter selection and multi-scale stability analysis, and consensus-based control strategies for the microgrid and microgrid clusters. The book will be an invaluable technical reference for practicing engineers and researchers working in the areas of renewable energy, power electronics, energy internet, and smart grid. It can also be utilized as reference book for undergraduate and postgraduate students in electrical engineering.

The concept of the smart grid promises the world an efficient and intelligent approach of managing energy production, transportation, and consumption by incorporating intelligence, efficiency, and optimality into the power grid. Both energy providers and consumers can take advantage of the convenience, reliability, and energy savings achieved by real-time and intelligent energy management. To this end, the current power grid is experiencing drastic changes and upgrades. For instance, more significant green energy resources such as wind power and solar power are being integrated into the power grid, and higher energy storage capacity is being installed in order to mitigate the intermittency issues brought about by the variable energy resources. At the same time, novel power electronics technologies and operating strategies are being invented and adopted. For instance, Flexible AC transmission systems and phasor measurement units are two promising technologies for improving the power system reliability and power quality. Demand side management will enable the customers to manage the power loads in an active fashion. As a result, modeling and control of modern power grids pose great challenges due to the adoption of new smart grid technologies. In this book, chapters regarding representative applications of smart grid technologies written by world-renowned experts are included, which explain in detail various innovative modeling and control methods.

This book is focused on the fundamental aspects of analysis, modeling and design of digital control loops around high-frequency switched-mode power converters in a systematic and rigorous manner Comprehensive treatment of digital control theory for power converters Verilog and VHDL sample codes are provided Enables readers to successfully analyze, model, design, and implement voltage, current, or multi-loop digital feedback loops around switched-mode power converters Practical examples are used throughout the book to illustrate applications of the techniques developed Matlab examples are also provided

Modeling and Control of Power Electronics Converter Systems for Power Quality Improvements provides grounded theory for the modeling, analysis and control of different converter topologies that improve the power quality of mains. Intended for researchers and practitioners working in the field, topics include modeling equations and the state of research to improve power quality converters. By presenting control methods for different converter topologies and aspects related to multi-level inverters and specific analysis related to the AC interface of drives, the book helps users by putting a particular emphasis on different control algorithms that enhance knowledge and research work. Present In-depth coverage of modeling and control methods for different converter topology Includes a particular emphasis on different control algorithms to give readers an easier understanding Provides a results and discussion chapter and MATLAB simulation to support worked examples and real-life application scenarios