Multi-terminal High-voltage Converter


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.




Design, Control, and Application of Modular Multilevel Converters for HVDC Transmission Systems


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.




High Voltage Direct Current Transmission


Book Description

Presents the latest developments in switchgear and DC/DC converters for DC grids, and includes substantially expanded material on MMC HVDC This newly updated edition covers all HVDC transmission technologies including Line Commutated Converter (LCC) HVDC; Voltage Source Converter (VSC) HVDC, and the latest VSC HVDC based on Modular Multilevel Converters (MMC), as well as the principles of building DC transmission grids. Featuring new material throughout, High Voltage Direct Current Transmission: Converters, Systems and DC Grids, 2nd Edition offers several new chapters/sections including one on the newest MMC converters. It also provides extended coverage of switchgear, DC grid protection and DC/DC converters following the latest developments on the market and in research projects. All three HVDC technologies are studied in a wide range of topics, including: the basic converter operating principles; calculation of losses; system modelling, including dynamic modelling; system control; HVDC protection, including AC and DC fault studies; and integration with AC systems and fundamental frequency analysis. The text includes: A chapter dedicated to hybrid and mechanical DC circuit breakers Half bridge and full bridge MMC: modelling, control, start-up and fault management A chapter dedicated to unbalanced operation and control of MMC HVDC The advancement of protection methods for DC grids Wideband and high-order modeling of DC cables Novel treatment of topics not found in similar books, including SimPowerSystems models and examples for all HVDC topologies hosted by the 1st edition companion site. High Voltage Direct Current Transmission: Converters, Systems and DC Grids, 2nd Edition serves as an ideal textbook for a graduate-level course or a professional development course.




Planning and Control of Expandable Multi-Terminal VSC-HVDC Transmission Systems


Book Description

This book discusses novel methods for planning and coordinating converters when an existing point-to-point (PtP) HVDC link is expanded into a multi-terminal HVDC (MTDC) system. It demonstrates that expanding an existing PtP HVDC link is the best way to build an MTDC system, and is especially a better option than the build-from-scratch approach in cases where several voltage-sourced converter (VSC) HVDC links are already in operation. The book reports in detail on the approaches used to estimate the new steady-state operation limits of the expanded system and examines the factors influencing them, revealing new operation limits in the process. Further, the book explains how to coordinate the converters to stay within the limits after there has been a disturbance in the system. In closing, it describes the current DC grid control concept, including how to implement it in an MTDC system, and introduces a new DC grid control layer, the primary control interface (IFC).




Design, Control and Protection of Modular Multilevel Converter (MMC)-based Multi-terminal HVDC System


Book Description

Even though today's transmission grids are predominantly based on the high voltage alternating current (HVAC) scheme, interests on high voltage direct current (HVDC) are growing rapidly during the past decade, due to the increased penetration of remote renewable energy. Voltage source converter (VSC) type is preferred over the traditional line-commutated converter (LCC) for this application, due to the advantages like smaller station footprint and no need for strong interfacing ac grid. As the state-of-the-art VSC topology, modular multilevel converter (MMC) is mostly considered. Most renewable energy sources, such as wind and solar, is usually sparsely located. Multi-terminal HVDC (MTDC) provides better use of transmission infrastructure, higher transmission flexibility and reliability, than building multiple point-to-point HVDCs. This dissertation studies the MMC-based MTDC system, including design, control and protection. Passive components design methodology in MMC is developed, with practical consideration. The developed arm inductance selection criterion considers the implementation of circulating current suppression control. And the unbalanced voltage among submodule capacitor is taken into account for submodule capacitance design. Circulating current suppression control is found to impact the MMC operating range. The maximum modulation index reduction is calculated utilizing a decoupled MMC model. A four-terminal HVDC testbed is developed, with similar control and communication architectures of the practical projects implemented. Several most typical operation scenarios and controls are demonstrated or proposed. In order to allow HVDC disconnects to online trip a line, dc line current control is proposed through station control. Utilizing the dc line current control, an automatic dc line current limiting control is proposed. Both controls have been verified in the developed testbed. A systematic dc fault protection strategy of MTDC utilizing hybrid dc circuit breaker is developed, including a new fast and selective fault detection method taking advantage of the hybrid dc circuit breaker special operation mechanism. Detailed criteria and control methods to assist system recovery are presented. A novel fault tolerant MMC topology is proposed with a hybrid submodule by adding an ultra-fast mechanical switch. The converter power loss can be almost the same as the half-bridge MMC, and 1/3 reduction compared to the similar clamp-double topology.




Multi-terminal Direct-Current Grids


Book Description

A generic DC grid model that is compatible with the standard AC system stability model is presented and used to analyse the interaction between the DC grid and the host AC systems. A multi-terminal DC (MTDC) grid interconnecting multiple AC systems and offshore energy sources (e.g. wind farms) across the nations and continents would allow effective sharing of intermittent renewable resources and open market operation for secure and cost-effective supply of electricity. However, such DC grids are unprecedented with no operational experience. Despite lots of discussions and specific visions for setting up such MTDC grids particularly in Europe, none has yet been realized in practice due to two major technical barriers: Lack of proper understanding about the interaction between a MTDC grid and the surrounding AC systems. Commercial unavailability of efficient DC side fault current interruption technology for conventional voltage sourced converter systems This book addresses the first issue in details by presenting a comprehensive modeling, analysis and control design framework. Possible methodologies for autonomous power sharing and exchange of frequency support across a MTDC grid and their impact on overall stability is covered. An overview of the state-of-the-art, challenges and on-going research and development initiatives for DC side fault current interruption is also presented.




Self-Commutating Converters for High Power Applications


Book Description

For very high voltage or very high current applications, the power industry still relies on thyristor-based Line Commutated Conversion (LCC), which limits the power controllability to two quadrant operation. However, the ratings of self-commutating switches such as the Insulated-Gate Bipolar Transistor (IGBT) and Integrated Gate-Commutated Thyristor (IGCT), are reaching levels that make the technology possible for very high power applications. This unique book reviews the present state and future prospects of self-commutating static power converters for applications requiring either ultra high voltages (over 600 kV) or ultra high currents (in hundreds of kA). It is an important reference for electrical engineers working in the areas of power generation, transmission and distribution, utilities, manufacturing and consulting organizations. All topics in this area are held in this one complete volume. Within these pages, expect to find thorough coverage on: modelling and control of converter dynamics; multi-level Voltage Source Conversion (VSC) and Current Source Conversion (CSC); ultra high-voltage VSC and CSC DC transmission; low voltage high DC current AC-DC conversion; industrial high current applications; power conversion for high energy storage. This text has a host of helpful material that also makes it a useful source of knowledge for final year engineering students specializing in power engineering, and those involved in postgraduate research.




Multilevel Voltage Source Converters in High Voltage Direct Current Transmission Systems


Book Description

This research focuses on voltage source multilevel converters in high voltage direct current (HVDC) transmission systems. The first Voltage Source Converter based HVDC (VSC-HVDC) systems with series connected IGBTs in a two-level converter represented a solution to meet industrial and economical requirements but is associated with significant drawbacks such as high dv/dt and di/dt, high switching loss, and poor output voltage and current quality. To overcome these issues, the multilevel converter was proposed for HVDC application. The Modular Multilevel Converter (M2C) was the first multilevel converter to be commercially used in the power industry. In this thesis, the M2C is investigated mainly in terms of operating principle, capacitor size and capacitor voltage ripple, capacitor voltage balancing technique and modulation scheme. The results of this investigation show that the M2C offers the following features: improved efficiency, lower supporting voltage and current in the switching devices and low dv/dt. These features make the M2C suitable for HVDC systems. Two new operational principles and modulation strategies for a Hybrid Cascaded Multilevel Converter (HCMC) are proposed in this thesis. Both modulation schemes extend the modulation index linear range and improve the output waveform quality. This gives the HCMC a higher power density than any known multilevel converter topology for the same dc link voltage and switching device rating. Simulations for both types of multilevel converter (M2C and HCMC) are supported by practical results from scaled hardware laboratory converters. Mathematical analysis and calculation of conversion loss for both types of multilevel converter and for the conventional two-level converter are performed. It is shown that both M2C and HCMC provide lower conversion loss compare to the conventional two-level converter. A control strategy for these two multilevel converters in point-to-point and multi-terminal HVDC systems is also studied. Simulation results show that these two converters are able to operate over the entire specified P-Q capability curve and are capable of riding through ac faults without imposing any over-voltage or over-current on the converter switches.




Power System Modeling, Computation, and Control


Book Description

Provides students with an understanding of the modeling and practice in power system stability analysis and control design, as well as the computational tools used by commercial vendors Bringing together wind, FACTS, HVDC, and several other modern elements, this book gives readers everything they need to know about power systems. It makes learning complex power system concepts, models, and dynamics simpler and more efficient while providing modern viewpoints of power system analysis. Power System Modeling, Computation, and Control provides students with a new and detailed analysis of voltage stability; a simple example illustrating the BCU method of transient stability analysis; and one of only a few derivations of the transient synchronous machine model. It offers a discussion on reactive power consumption of induction motors during start-up to illustrate the low-voltage phenomenon observed in urban load centers. Damping controller designs using power system stabilizer, HVDC systems, static var compensator, and thyristor-controlled series compensation are also examined. In addition, there are chapters covering flexible AC transmission Systems (FACTS)—including both thyristor and voltage-sourced converter technology—and wind turbine generation and modeling. Simplifies the learning of complex power system concepts, models, and dynamics Provides chapters on power flow solution, voltage stability, simulation methods, transient stability, small signal stability, synchronous machine models (steady-state and dynamic models), excitation systems, and power system stabilizer design Includes advanced analysis of voltage stability, voltage recovery during motor starts, FACTS and their operation, damping control design using various control equipment, wind turbine models, and control Contains numerous examples, tables, figures of block diagrams, MATLAB plots, and problems involving real systems Written by experienced educators whose previous books and papers are used extensively by the international scientific community Power System Modeling, Computation, and Control is an ideal textbook for graduate students of the subject, as well as for power system engineers and control design professionals.