Advanced Control Architectures For Grid Connected And Standalone Converter Systems

"This dissertation proposes new control algorithms dedicated towards improving the reliability, computational burden and stability in grid-connected and stand-alone based power electronic converter systems applicable for ac microgrids. Two voltage sensorless control architectures, one for stand-alone applications and the other for grid-connected application are established in this thesis. The output voltage of a standalone single-phase inverter is controlled directly by controlling the output filter capacitor current without using a dedicated output voltage sensor. A method to estimate the output filter capacitance is also presented. For the grid connected converter, a novel closed loop estimation is presented to estimate the grid voltage. In addition to the estimation of the grid voltage, the proposed method also generates the unit vectors and frequency information similar to a conventional phase-locked loop structure. The voltage sensorless algorithm is then extended to LCL filter based grid connected converters thereby proposing a new indirect method of controlling the grid current. Furthermore, addressing the stability issues in current-controlled grid tied converters, this dissertation also analyzes the power angle synchronization control of grid-tied bidirectional converters for low voltage grids. The power flow equations for the low voltage grid are analyzed and compensators are designed to ensure the decoupled control of active and reactive power. It is demonstrated that the proposed compensators are immune to grid fluctuations and ensure stable operation controlling the desired power flow to and from the grid. Detailed plant modeling, controller design, simulation and experimental results are presented for all of the proposed schemes"--Abstract, page iv.

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

With the progressive rise of the micro-grids incorporating renewable energy sources, a new electricity distribution paradigm is emerging. These new architectures interface uncontrolled consumers with intermittent energy sources, therefore imposing more stress on the conversion, storage and management of the energy.Power converters are adapting accordingly, in particular, with the development of multi-level converters, which allow higher power rates and better power quality than their predecessors with similar components, but whose control is becoming increasingly complex.Due to their hybrid nature, the control of power converters is traditionally split into two parts: on the one side, the continuous objectives related to the main interfacing function of the power converters, and, on the other side, the driving of their quantized power switches, known as the modulation strategy.In this context, the growing demands in efficiency, reliability, versatility and performance require a high level of intelligence of the complete control structure. To meet these requirements, the objectives of this research work are to address both the interfacing objectives and the inner driving of the converter into a single controller. This decision implies incorporating the non-linearity of power converters into the controller, equivalent to suppressing the traditional modulation block. Modulation is the traditional solution to linearize the inner operation of the converters. The Model Predictive Control (MPC) approach was chosen to handle the non-linearity and the diversity of control objectives that accompany power converters.The developed control algorithm combines graph theory, with Dijkstra, A* and other algorithms, with a special state-space model designed for switching systems to form a powerful universal tool capable of simultaneously manipulating the discrete and continuous nature of the converter and its environment. Switched state-space models are studied, leading to interesting results on stability and controllability concerning their application on power converters.The obtained controller is then tested in simulation, with various case studies: grid-connected and standalone inverter, rectifier and bidirectional operation. These situations are studied for three common multi-level topologies: Neutral Point-Clamped, Flying Capacitor and Cascaded H-Bridge. The exact same MPC structure is used for each and every one of the case studies, with adaptations of its internal behavior. This behavior is agglomerated in two functions: the prediction, containing the model of the converter, and the cost function, which translates the control requirements into the optimal problem solved by the algorithm. Changing the topology implies adjusting the model, without impacting the cost function, while modifying this function is sufficient to adapt to the different applications.The results show that the controller manages to directly drive the power switches according to the application, demonstrating a large variety of considerations and objectives. The overall performance of this unique structure is comparable to that of the multiple structures used for each of the studied cases, with the notable exception of rectifier operation mode, where the speed and range of possibilities are particularly interesting.In conclusion, the developed controller manages miscellaneous applications, topologies, objectives and constraints. While the traditional linear control structures have to change, often deeply, for different operation modes and control requirements, such modifications do not affect the control architecture of the designed MPC controller. This shows the versatility of the proposed solution and its universality, further demonstrated by its ability to adapt to different power converters without modifications. Finally, the complexity of the modulation is fully included in the structure, offering simplicity and flexibility to the control design.

The high-power grid-connected converters play a vital role in modern power system, realizing the conversion and transmission of electrical energy, and determining its safety, stability and efficiency. This book explores the advanced control strategies of high-power grid-connected converter to satisfy the high-power requirements in practical applications. Special attention is given to grid-connected converter modules in parallel operation to overcome the challenges of non-ideal power grid, power switches faults, and circulating current. Through the advanced control strategies presented in this book, the power capacity of grid-connected converter is flexibly increased with high-reliability and efficiency, thus expanding the application range of high-power converters in modern power system. To facilitate understanding, this book provides step-by-step model derivation and controller design for grid-connected converter. Meanwhile, it also provides the comprehensive simulation and experimental results to offer readers a deep insight into the control process of grid-connected converters. This book serves as a guide for electrical engineers and researchers involved in the development of high-power converters.

This book presents ongoing research activities of currently available renewable energy technologies and the approaches towards clean technology for enabling a socio-economic model for the present and future generations to live in a clean and healthy environment. The book provides chapter wise implementation of research works in the area of green energy technologies with proper methods used with solution strategies and energy efficiency approaches by combining theory and practical applications. Readers are introduced to practical problems of green computation and hybrid resources optimization with solution based approaches from the current research outcomes. The book will be of use to researchers, professionals, and policy-makers alike.

Control of Standalone Microgrid looks at a practical and systematic elaboration of the architecture, design and control of standalone microgrids. It is oriented towards more advanced readers who want to enhance their knowledge in the fields of power engineering, sustainable energy, microgrids and their control. With an enriched collection of topics pertaining to the architecture and control of standalone microgrids, this book presents recent research that will bring advancements in the current power system scenario, discussing operational and technical issues due to high penetration of distributed generation units. Including executable plans for standalone microgrid systems this book enables researchers and energy executives to understand the future of energy delivery systems as well as global case studies and models to apply control techniques for standalone microgrids and protection schemes which provide a deeper level of understanding. Includes significant case studies and global case studies of control techniques and protection schemes Provides a working guideline in the design, analysis and development of Standalone microgrid and its applications Features detailed description of the types and components of standalone microgrids, modeling and simulation and performance analysis

This textbook is intended for engineering students taking courses in power electronics, renewable energy sources, smart grids or static power converters. It is also appropriate for students preparing a capstone project where they need to understand, model, supply, control and specify the grid side power converters. The main goal of the book is developing in students the skills that are required to design, control and use static power converters that serve as an interface between the ac grid and renewable power sources. The same skills can be used to design, control and use the static power converters used within the micro-grids and nano-grids, as the converters that provide the interface between such grids and the external grid. The author’s approach starts with basic functionality and the role of grid connected power converters in their typical applications, and their static and dynamic characteristics. Particular effort is dedicated to developing simple, concise, intuitive and easy-to-use mathematical models that summarize the essence of the grid side converter dynamics. Mathematics is reduced to a necessary minimum, solved examples are used extensively to introduce new concepts, and exercises are used to test mastery of new skills.

​​Series-Parallel Converter-Based Microgrids: System-Level Control and Stability is the first book to provide a comprehensive and in-depth introduction to the rapid development of series-parallel converter applications in the microgrid system. It provides an advanced and in-depth introduction into all major system modeling, coordinated control, and stability analysis issues, and provides useful methodologies and philosophies for developing new topologies and controls for self-organized decentralized operation of microgrid systems. For each topic, a theoretical introduction and overview are backed by very concrete programming examples that enable the reader to not only understand the topic but to develop microgrid simulation models.

A comprehensive survey of advanced multilevel converter design, control, operation and grid-connected applications Advanced Multilevel Converters and Applications in Grid Integration presents a comprehensive review of the core principles of advanced multilevel converters, which require fewer components and provide higher power conversion efficiency and output power quality. The authors – noted experts in the field – explain in detail the operation principles and control strategies and present the mathematical expressions and design procedures of their components. The text examines the advantages and disadvantages compared to the classical multilevel and two level power converters. The authors also include examples of the industrial applications of the advanced multilevel converters and offer thoughtful explanations on their control strategies. Advanced Multilevel Converters and Applications in Grid Integration provides a clear understanding of the gap difference between research conducted and the current industrial needs. This important guide: Puts the focus on the new challenges and topics in related areas such as modulation methods, harmonic analysis, voltage balancing and balanced current injection Makes a strong link between the fundamental concepts of power converters and advances multilevel converter topologies and examines their control strategies, together with practical engineering considerations Provides a valid reference for further developments in the multilevel converters design issue Contains simulations files for further study Written for university students in electrical engineering, researchers in areas of multilevel converters, high-power converters and engineers and operators in power industry, Advanced Multilevel Converters and Applications in Grid Integration offers a comprehensive review of the core principles of advanced multilevel converters, with contributions from noted experts in the field.

To meet the increasing demand of electrical power, the use of renewable energy-based smart grid is attracting significant attention in recent years throughout the world. The high penetration of renewable power in the smart grids is growing its importance due to its non-finishing, reusable, reliable, sustainable, lower cost, and available characteristics. The renewable energy-based smart grid technology may mitigate the increasing energy demands effectively and efficiently without hampering the environment. But the uncertain nature of renewable sources largely affects the operation of the smart grid by un-stabling the voltage and frequency that may introduces power quality and reliability problems, which requires special control techniques. This book investigates the challenges in controlling renewable energy-based smart grids and proposes different control techniques to control the voltage and frequency effectively to improve the power quality and reliability of the power grids. This book is a valuable resource for readers interested in practical solutions in smart grids and renewable energy systems.