Design, Analysis, and Control of the Modular Multilevel DC/DC Converter for Medium- and High-voltage DC Grids PDF Download
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Author: Ramin Razani Publisher: ISBN: Category : DC-to-DC converters Languages : en Pages : 0
Book Description
Nowadays, renewable energy sources have gained escalating importance due to environmental and economic reasons. However, these energy sources are primarily located in remote areas and distant from load centers. High-voltage dc (HVDC) and medium-voltage dc (MVDC) systems have been proposed in the last decades for efficient and reliable integration of renewable energy resources. To date, a noticeable number of these dc systems are established around the world. Recently, researchers have proposed the concept of "DC grids," which can be realized by connecting the existing point-to-point dc systems. This structure can improve the efficiency and stability of the power system. However, one of the most concerning challenges related to this concept is the interconnection of already built dc systems. Because existing dc systems are built through time, they possibly have different voltage levels and grounding systems. To address this challenge, the dc/dc modular multilevel converter (MMC) is proposed in the literature as one of the most promising solutions. This converter offers the advantages of modularity, scalability, and high efficiency. Few studies have been conducted on the modeling and control of the dc/dc MMC. The literature falls short in several aspects, such as improved design, analysis of operation limits, fault-tolerant operation, converter analysis under uncertainty, and development of advanced controllers and efficient fault-blocking capability. This research aims to 1) develop an augmented design approach that considers both control and hardware aspects of the converter, 2) investigate the operation limit of the hybrid dc/dc MMC caused by the capacitors voltages unbalance, 3) develop a tailored fault-tolerant operation strategy without additional submodules (SMs), 4) analyze the unsymmetrical operation of the dc/dc MMC caused by parametric uncertainty, 5) develop an advanced controller based on the model predictive control for the dc/dc MMC, and 6) realize an efficient fault-blocking capability by proper selection of SMs. The first study in this thesis facilitates the dc/dc MMC design with a smaller number of SMs and higher efficiency. Unlike the previous literature, the analytical results of the second study show that the capacitors voltages balance in the hybrid dc/dc MMC limits the operation range of the converter. In the third study, first, the unique features of the dc/dc MMC are investigated. These features make the fault-tolerant operation possible without the need for additional SMs. Then, utilizing these features, a tailored fault-tolerant operation strategy is developed to cope with several SMs failures. When the parametric uncertainty comes into action, it can force the converter to work in unsymmetrical conditions. The fourth study develops steady-state models representing the behavior of the converter in unsymmetrical conditions, and then the maximum tolerable variation of parameters is found in different practical cases. An advanced controller based on the model predictive control is developed in the fifth study to improve the steady-state and transient performances of the dc/dc MMC. Finally, an efficient fault-blocking capability is realized by adequately selecting the number and type of SMs. Detailed time-domain simulations under the MATLAB/Simulink environment validate the analytical results. This research contributed to the fundamental understanding of the dc/dc MMC operation and significantly improved the converter efficiency, reliability, and steady-state and dynamic performances.
Author: Ramin Razani Publisher: ISBN: Category : DC-to-DC converters Languages : en Pages : 0
Book Description
Nowadays, renewable energy sources have gained escalating importance due to environmental and economic reasons. However, these energy sources are primarily located in remote areas and distant from load centers. High-voltage dc (HVDC) and medium-voltage dc (MVDC) systems have been proposed in the last decades for efficient and reliable integration of renewable energy resources. To date, a noticeable number of these dc systems are established around the world. Recently, researchers have proposed the concept of "DC grids," which can be realized by connecting the existing point-to-point dc systems. This structure can improve the efficiency and stability of the power system. However, one of the most concerning challenges related to this concept is the interconnection of already built dc systems. Because existing dc systems are built through time, they possibly have different voltage levels and grounding systems. To address this challenge, the dc/dc modular multilevel converter (MMC) is proposed in the literature as one of the most promising solutions. This converter offers the advantages of modularity, scalability, and high efficiency. Few studies have been conducted on the modeling and control of the dc/dc MMC. The literature falls short in several aspects, such as improved design, analysis of operation limits, fault-tolerant operation, converter analysis under uncertainty, and development of advanced controllers and efficient fault-blocking capability. This research aims to 1) develop an augmented design approach that considers both control and hardware aspects of the converter, 2) investigate the operation limit of the hybrid dc/dc MMC caused by the capacitors voltages unbalance, 3) develop a tailored fault-tolerant operation strategy without additional submodules (SMs), 4) analyze the unsymmetrical operation of the dc/dc MMC caused by parametric uncertainty, 5) develop an advanced controller based on the model predictive control for the dc/dc MMC, and 6) realize an efficient fault-blocking capability by proper selection of SMs. The first study in this thesis facilitates the dc/dc MMC design with a smaller number of SMs and higher efficiency. Unlike the previous literature, the analytical results of the second study show that the capacitors voltages balance in the hybrid dc/dc MMC limits the operation range of the converter. In the third study, first, the unique features of the dc/dc MMC are investigated. These features make the fault-tolerant operation possible without the need for additional SMs. Then, utilizing these features, a tailored fault-tolerant operation strategy is developed to cope with several SMs failures. When the parametric uncertainty comes into action, it can force the converter to work in unsymmetrical conditions. The fourth study develops steady-state models representing the behavior of the converter in unsymmetrical conditions, and then the maximum tolerable variation of parameters is found in different practical cases. An advanced controller based on the model predictive control is developed in the fifth study to improve the steady-state and transient performances of the dc/dc MMC. Finally, an efficient fault-blocking capability is realized by adequately selecting the number and type of SMs. Detailed time-domain simulations under the MATLAB/Simulink environment validate the analytical results. This research contributed to the fundamental understanding of the dc/dc MMC operation and significantly improved the converter efficiency, reliability, and steady-state and dynamic performances.
Author: Sixing Du Publisher: John Wiley & Sons ISBN: 1119366305 Category : Science Languages : en Pages : 360
Book Description
An invaluable academic reference for the area of high-power converters, covering all the latest developments in the field High-power multilevel converters are well known in industry and academia as one of the preferred choices for efficient power conversion. Over the past decade, several power converters have been developed and commercialized in the form of standard and customized products that power a wide range of industrial applications. Currently, the modular multilevel converter is a fast-growing technology and has received wide acceptance from both industry and academia. Providing adequate technical background for graduate- and undergraduate-level teaching, this book includes a comprehensive analysis of the conventional and advanced modular multilevel converters employed in motor drives, HVDC systems, and power quality improvement. Modular Multilevel Converters: Analysis, Control, and Applications provides an overview of high-power converters, reference frame theory, classical control methods, pulse width modulation schemes, advanced model predictive control methods, modeling of ac drives, advanced drive control schemes, modeling and control of HVDC systems, active and reactive power control, power quality problems, reactive power, harmonics and unbalance compensation, modeling and control of static synchronous compensators (STATCOM) and unified power quality compensators. Furthermore, this book: Explores technical challenges, modeling, and control of various modular multilevel converters in a wide range of applications such as transformer and transformerless motor drives, high voltage direct current transmission systems, and power quality improvement Reflects the latest developments in high-power converters in medium-voltage motor drive systems Offers design guidance with tables, charts graphs, and MATLAB simulations Modular Multilevel Converters: Analysis, Control, and Applications is a valuable reference book for academic researchers, practicing engineers, and other professionals in the field of high power converters. It also serves well as a textbook for graduate-level students.
Author: Kamran Sharifabadi Publisher: John Wiley & Sons ISBN: 1118851544 Category : Science Languages : en Pages : 522
Book Description
Design, Control and Application of Modular Multilevel Converters for HVDC Transmission Systems is a comprehensive guide to semiconductor technologies applicable for MMC design, component sizing control, modulation, and application of the MMC technology for HVDC transmission. Separated into three distinct parts, the first offers an overview of MMC technology, including information on converter component sizing, Control and Communication, Protection and Fault Management, and Generic Modelling and Simulation. The second covers the applications of MMC in offshore WPP, including planning, technical and economic requirements and optimization options, fault management, dynamic and transient stability. Finally, the third chapter explores the applications of MMC in HVDC transmission and Multi Terminal configurations, including Supergrids. Key features: Unique coverage of the offshore application and optimization of MMC-HVDC schemes for the export of offshore wind energy to the mainland. Comprehensive explanation of MMC application in HVDC and MTDC transmission technology. Detailed description of MMC components, control and modulation, different modeling approaches, converter dynamics under steady-state and fault contingencies including application and housing of MMC in HVDC schemes for onshore and offshore. Analysis of DC fault detection and protection technologies, system studies required for the integration of HVDC terminals to offshore wind power plants, and commissioning procedures for onshore and offshore HVDC terminals. A set of self-explanatory simulation models for HVDC test cases is available to download from the companion website. This book provides essential reading for graduate students and researchers, as well as field engineers and professionals who require an in-depth understanding of MMC technology.
Author: Bo Zhang Publisher: John Wiley & Sons ISBN: 1119188350 Category : Science Languages : en Pages : 226
Book Description
An all-in-one guide to high-voltage, multi-terminal converters, this book brings together the state of the art and cutting-edge techniques in the various stages of designing and constructing a high-voltage converter. The book includes 9 chapters, and can be classified into three aspects. First, all existing high-voltage converters are introduced, including the conventional two-level converter, and the multi-level converters, such as the modular multi-level converter (MMC). Second, different kinds of multi-terminal high-voltage converters are presented in detail, including the topology, operation principle, control scheme and simulation verification. Third, some common issues of the proposed multi-terminal high-voltage converters are discussed, and different industrial applications of the proposed multi-terminal high-voltage converters are provided. Systematically proposes, for the first time, the design methodology for high-voltage converters in use of MTDC grids; also applicable to constructing novel power electronics converters, and driving the development of HVDC, which is one of the most important technology areas Presents the latest research on multi-terminal high-voltage converters and its application in MTDC transmission systems and other industrially important applications Offers an overview of existing technology and future trends of the high-voltage converter, with extensive discussion and analysis of different types of high-voltage converters and relevant control techniques (including DC-AC, AC-DC, DC-DC, and AC-AC converters) Provides readers with sufficient context to delve into the more specialized topics covered in the book Featuring a series of novel multi-terminal high-voltage converters proposed and patented by the authors, Multi-terminal High Voltage Converters is written for researchers, engineers, and advanced students specializing in power electronics, power system engineering and electrical engineering.
Author: Islam Azmy Gowaid Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
DC fault protection is one challenge impeding the development of multi-terminal dc grids. The absence of manufacturing and operational standards has led to many point-to-point HVDC links built at different voltage levels, which creates another challenge. Therefore, the issues of voltage matching and dc fault isolation in high voltage dc systems are undergoing extensive research and are the focus of this thesis. The modular multilevel design of dual active bridge (DAB) converters is analysed in light of state-of-the-art research in the field. The multilevel DAB structure is meant to serve medium and high voltage applications. The modular design facilitates scalability in terms of manufacturing and installation, and permits the generation of an output voltage with controllable dv/dt. The modular design is realized by connecting an auxiliary soft voltage clamping circuit across each semiconductor switch (for instance insulated gate bipolar transistor - IGBT) of the series switch arrays in the conventional two-level DAB design. With auxiliary active circuits, series connected IGBTs effectively become series connection of half-bridge submodules (cells) in each arm, resembling the modular multilevel converter (MMC) structure. For each half-bridge cell, capacitance for quasi-square wave (quasi two- level) operation is significantly smaller than typical capacitance used in MMCs. Also, no bulky arm inductors are needed. Consequently, the footprint, volume, weight and cost of cells are lower. Four switching sequences are proposed and analysed in terms of switching losses and operation aspects. A design method to size converter components is proposed and validated. Soft-switching characteristics of the analysed DAB are found comparable to the case of a two-level DAB at the same ratings and conditions. A family of designs derived from the proposed DAB design are studied in depth. Depending on the individual structure, they may offer further advantages in term of installed semiconductor power, energy storage, conduction losses, or footprint. A non-isolated dc-dc converter topology which offers more compact and efficient station design with respect to isolated DAB - yet without galvanic isolation - is studied for quasi two-level (trapezoidal) operation and compared to the isolated versions. In all the proposed isolated designs, active control of the dc-dc converter facilitates dc voltage regulation and near instant isolation of pole-to-pole and pole-to-ground dc faults within its protection zone. The same can be achieved for the considered non-isolated dc-dc converter topology with additional installed semiconductors. Simulation and experimental results are presented to substantiate the proposed concepts.
Author: Fujin Deng Publisher: John Wiley & Sons ISBN: 1119875625 Category : Technology & Engineering Languages : en Pages : 372
Book Description
Modular Multilevel Converters Expert discussions of cutting-edge methods used in MMC control, protection, and fault detection In Modular Multilevel Converters: Control, Fault Detection, and Protection, a team of distinguished researchers delivers a comprehensive discussion of fault detection, protection, and tolerant control of modular multilevel converters (MMCs) under internal and external faults. Beginning with a description of the configuration of MMCs, their operation principles, modulation schemes, mathematical models, and component design, the authors go on to explore output control, fault detection, capacitor monitoring, and other topics of central importance in the field. The book offers summaries of centralized capacitor voltage-balancing control methods and presents several capacitor monitoring methods, like the direct and sorting-based techniques. It also describes full-bridge and half-bridge submodule-based hybrid MMC protection methods and alternative fault blocking SM-based MMCs. Readers will also find: A thorough introduction to modular multilevel converters, including circuits, operation principles, modulation, mathematical models, components, and design constraints In-depth discussions of the control of modular multilevel converters, including output control, centralized capacitor voltage control, and individual capacitor voltage control Comprehensive explorations of fault detection of MMCs under IGBT faults, including short-circuit and open-circuit faults, as well as fault-tolerant control of MMCs Fulsome treatments of the control of MMCs under AC grid faults, including discussions of AC-side current control Perfect for electrical engineering researchers, Modular Multilevel Converters: Control, Fault Detection, and Protection, will also earn a place in the libraries of electrical engineers working in industry, as well as undergraduate and graduate students with an interest in MMCs.
Author: Jaydeep Saha Publisher: Springer Nature ISBN: 9811949026 Category : Technology & Engineering Languages : en Pages : 295
Book Description
This book presents novel contributions in the development of solid-state-transformer (SST) technology both for medium-voltage (MV) and low-voltage (LV) utility grid interfaces, which can potentially augment the grid modernization process in the evolving power system paradigm. For the MV interface, a single-stage AC-DC SST submodule topology has been proposed, and its modulation and soft-switching possibilities are analysed, experimentally validated and adequately benchmarked. A control scheme with power balance capability among submodules is developed for MV grid-connected single-stage AC-DC SST for smooth operation under inevitable parameter drift scenario, and experimental validation shows excellent performance under drastic load change conditions. A novel machine learning-aided multi-objective design optimization framework for grid-connected SST is developed and experimentally validated, which equips a power electronics design engineer with meagre computational resources to find out the most optimal SST design in a convenient time-frame. This book has also contributed towards the development of dual-active-bridge (DAB)-type and non-DAB-type LV grid-interfaced isolated AC-DC converters by providing solutions to specific topology and modulation-related shortcomings in these two types of topologies. A comprehensive comparison of the DAB and non-DAB-type LVAC-LVDC converters reveals the superiority of DAB-type conversion strategy.
Author: Zeng Rong Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
This thesis investigates the design, analysis, and operation of modular multilevel converters (MMC) for HVDC applications. Based on the operation principles of the MMC, the operation of MMC under asymmetrical arm impedance conditions is analysed using three equivalent sub-circuits at different freqeuncy. Detail analysis of the impact of asymmetrical conditions on the differential-mode current, the common-mode current and sub-module (SM) capacitor voltages, is performed. Based on the analysis, the corresponding control targets and an improved control strategy are designed to improve the operation performance. Considering the advantages of half-bridge based SM (HBSM) and full-bridge based SM (FBSM), a hybrid MMC (H-MMC) configuration consisting of FBSMs and HBSMs is proposed. By adopting the negative voltage state for some of the FBSMs, the output voltage range is extended to increase converter power transmission capability. By considering the relationships between the AC and DC voltages, AC, DC and arm currents, the ratio of the numbers of the FBSM to HBSM is analysed in order to maintain capacitor voltage balance and retain DC fault blocking capability. An equivalent circuit for the H-MMC is proposed, which considers each arm to be consisted of two individual voltage sources. This model is used to analyse SM capacitor voltage balancing and ripple. A two-stage selection and sorting algorithm is developed to ensure capacitor voltage balancing among the SMs. The proposed H-MMC is compared to other topologies in terms of power device utilization and power losses, and it shows that the H-MMC has higher device utilization and lower power loss than the conventional FBSM based MMC; Furthermore, The DC fault ride-through capability of the H-MMC are discussed. It is found that the H-MMC can not only isolate the DC fault, but also coniture operating at a wide DC voltage range from zero to rated value. Such two features of the H-MMC show the advantages in the hybrid configurations over the conventional FBSM and HBSM systems. Finally, two applications based on the proposed H-MMC are presented; one is a high power DC/DC converter with fault blocking capability for interconnecting large HVDC systems, and the other is a hybrid HVDC transmission system comprising a wind farm side VSC based on the H-MMC and a grid side LCC for transmitting wind power to AC grid.
Author: Ramin Razani
Author: Ramin Razani
Author: Sixing Du
Author: Kamran Sharifabadi
Author: Shenghui Cui
Author: Bo Zhang
Author: Wu Chen
Author: Islam Azmy Gowaid
Author: Fujin Deng
Author: Jaydeep Saha
Author: Zeng Rong