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

Kamran Sharifabadi, Power Grid & Regulatory Affairs, Statoil, Norway Kamran has twenty-five years of international experience in the field of HVDC technology projects. He started out as a research engineer in ABB and Siemen, worked as a consultant for five years, then became a manager at the Norwegian TSO. He is currently a senior technology advisor for Statoil`s HVDC projects, a guest lecturer in the topics of VSC HVDC, Wind power generation technologies at NTNU and at various different universities in central Europe. Kamran is an active member of the Cigre B4 (HVDC) working group and the leader of the steering committee for a European research project on DC grids.Remus Teodorescu, Aalborg University, Denmark Remus is an Associate Professor at the Institute of Technology, teaching courses in power electronics and electrical energy system control. He has authored over 80 journal and conference papers and two books. He is the founder and coordinator of the Green Power Laboratory at Aalborg University, and is co-recipient of the Technical Committee Prize Paper Award at IEEE Optim 2002.Hans Peter Nee, KTH, Sweden Hans is Professor of Power Electronics in the Department of Electrical Engineering. He has supervised and examined ten finalized doctor’s projects, and was awarded the Elforsk Scholarship in 1997. He has served on the board of the IEEE Sweden Section for many years and was Chairman during 2002 and 2003. He is also a member of EPE and serves in the Executive Council and in the International Steering Committee.Lennart Harnefors, ABB, Västerås, Sweden Lennart is currently with ABB Power Systems – HVDC, Ludvika, Sweden as an R&D Project Manager and Principal Engineer, and with KTH as an Adjunct Professor of power electronics. Between 2001 and 2005, he was a part-time Visiting Professor of electrical drives with Chalmers University of Technology, Sweden. He is an Associate Editor of the IEEE Transactions on Industrial Electronics, on the Editorial Board of IET Electric Power Applications, and a member of the Executive Council and the International Scientific Committee of the European Power Electronics and Drives Association.Staffan Norrga, KTH, Sweden Between 1994 and 2011, Staffan worked as a Development Engineer at ABB in Västerås, Sweden, in various power-electronics-related areas such as railway traction systems and converters for HVDC power transmission systems. In 2000, he returned to the Department of Electric Machines and Power Electronics of the Royal Institute of Technology, where he is an associate professor. He is the inventor or co-inventor of 11 granted patents and 14 patents pending and has authored more than 35 scientific papers.

• Preface xiiiAcknowledgements xvAbout the Companion Website xviiNomenclature xixIntroduction 11 Introduction to Modular Multilevel Converters 71.1 Introduction 71.2 The Two-Level Voltage Source Converter 91.3 Benefits of Multilevel Converters 151.4 Early Multilevel Converters 171.5 Cascaded Multilevel Converters 231.6 Summary 57References 582 Main-Circuit Design 602.1 Introduction 602.2 Properties and Design Choices of Power Semiconductor Devices for High-Power Applications 612.3 Medium-Voltage Capacitors for Submodules 922.4 Arm Inductors 962.5 Submodule Configurations 982.6 Choice of Main-Circuit Parameters 1122.7 Handling of Redundant and Faulty Submodules 1182.8 Auxiliary Power Supplies for Submodules 1212.9 Start-Up Procedures 1262.10 Summary 126References 1273 Dynamics and Control 1333.1 Introduction 1333.2 Fundamentals 1343.3 Converter Operating Principle and Averaged Dynamic Model 1373.4 Per-Phase Output-Current Control 1483.5 Arm-Balancing (Internal) Control 1613.6 Three-Phase Systems 1753.7 Vector Output-Current Control 1843.8 Higher-Level Control 1923.9 Control Architectures 2073.10 Summary 212References 2124 Control under Unbalanced Grid Conditions 2144.1 Introduction 2144.2 Grid Requirements 2144.3 Shortcomings of Conventional Vector Control 2154.4 Positive/Negative-Sequence Extraction 2194.5 Injection Reference Strategy 2234.6 Component-Based Vector Output-Current Control 2264.7 Summary 228References 2315 Modulation and Submodule Energy Balancing 2325.1 Introduction 2325.2 Fundamentals of Pulse-Width Modulation 2335.3 Carrier-Based Modulation Methods 2365.4 Multilevel Carrier-Based Modulation 2435.5 Nearest-Level Control 2525.6 Submodule Energy Balancing Methods 2565.7 Summary 270References 2716 Modeling and Simulation 2726.1 Introduction 2726.2 Leg-Level Averaged (LLA) Model 2746.3 Arm-Level Averaged (ALA) Model 2756.4 Submodule-Level Averaged (SLA) Model 2786.5 Submodule-Level Switched (SLS) Model 2806.6 Summary 281References 2827 Design and Optimization of MMC-HVDC Schemes for Offshore Wind-Power Plant Application 2837.1 Introduction 2837.2 The Influence of Regulatory Frameworks on the Development Strategies for Offshore HVDC Schemes 2847.3 Impact of Regulatory Frameworks on the Functional Requirements and Design of Offshore HVDC Terminals 2867.4 Components of an Offshore MMC-HVDC Converter 2877.5 Offshore Platform Concepts 2947.6 Onshore HVDC Converter 2957.7 Recommended System Studies for the Development and Integration of an Offshore HVDC Link to a WPP 2987.8 Summary 303References 3038 MMC-HVDC Standards and Commissioning Procedures 3058.1 Introduction 3058.2 CIGRE and IEC Activities for the Standardization of MMC-HVDC Technology 3068.3 MMC-HVDC Commissioning and Factory and Site Acceptance Tests 3098.4 Summary 317References 3179 Control and Protection of MMC-HVDC under AC and DC Network Fault Contingencies 3189.1 Introduction 3189.2 Two-Level VSC-HVDC Fault Characteristics under Unbalanced AC Network Contingency 3199.3 MMC-HVDC Fault Characteristics under Unbalanced AC Network Contingency 3229.4 dc Pole-to-Ground Short-Circuit Fault Characteristics of the Half-Bridge Mmc-hvdc 3259.5 MMC-HVDC Component Failures 3279.6 MMC-HVDC Protection Systems 3299.7 Summary 333References 33410 MMC-HVDC Transmission Technology and MTDC Networks 33610.1 Introduction 33610.2 LCC-HVDC Transmission Technology 33610.3 Two-Level VSC-HVDC Transmission Technology 33810.4 Modular Multilevel HVDC Transmission Technology 33910.5 The European HVDC Projects and MTDC Network Perspectives 34310.6 Multi-Terminal HVDC Configurations 34510.7 dc Load Flow Control in MTdc Networks 34810.8 dc Grid Control Strategies 34910.9 dc Fault Detection and Protection in MTdc Networks 35510.10 Fault-Detection Methods in MTDC 35710.11 dc Circuit Breaker Technologies 36210.12 Fault-Current Limiters 36710.13 The Influence of Grounding Strategy on Fault Currents 36910.14 dc Supergrids of the Future 37010.15 Summary 371References 371Index 373