Modular Multilevel Converters

Sixing Du, PhD, is a Postdoctoral Fellow in the Department of Electrical and Computer Engineering at Ryerson University in Toronto, Canada. Apparao Dekka, PhD, is a Postdoctoral Fellow in the Department of Electrical and Computer Engineering at Ryerson University in Toronto, Canada. He has made significant contributions to the control and application of the MMCs. Bin Wu, PhD, is a Professor in the Department of Electrical and Computer Engineering at Ryerson University in Toronto, Canada. He is a co-author of several Wiley-IEEE Press books. Navid Zargari, PhD, is a Manager & Product Architect in MV Drives R&D at Rockwell Automation, Toronto, Canada. He is a co-author of the Wiley publication Power Conversion and Control of Wind Energy Systems.

• About the Authors xiiiPreface xviiAcknowledgments xxiAcronyms xxiiiSymbols xxviiAbout the Companion Website xliPart I General Aspects of Conventional mmc1 Review of High-Power Converters 31.1 Introduction 31.2 Overview of High-Power Converters 41.3 Voltage Source Converters 61.3.1 Neutral-Point Clamped Converter 81.3.2 Active Neutral-Point Clamped Converter 101.3.3 Flying Capacitor Converter 111.3.4 Nested Neutral-Point Clamped Converter 121.3.5 Cascaded H-bridge Converter 131.3.6 Cascaded Neutral-Point Clamped Converter 151.4 Current Source Converters 161.4.1 Load-Commutated Current Source Converter 161.4.2 PWM Current Source Converter 181.5 Matrix Converters 191.5.1 Direct Matrix Converter 191.5.2 Indirect Matrix Converter 201.5.3 Multi-Modular Matrix Converter 211.6 Modular Multilevel Converters 231.6.1 Converter Technology 241.6.2 Applications 241.6.3 Technical Challenges 311.7 Summary 33References 342 Fundamentals of Modular Multilevel Converter 372.1 Introduction 372.2 Modular Multilevel Converter 382.2.1 Converter Con guration 392.2.2 Con guration of Submodules 392.2.3 Comparison of Submodules 462.2.4 Principle of Operation 482.3 Pulse Width Modulation Schemes 492.3.1 Phase-Shifted Carrier Modulation 512.3.2 Level-Shifted Carrier Modulation 592.3.3 Sampled Average Modulation 602.3.4 Space Vector Modulation 652.3.5 Staircase Modulation 732.4 Summary 77References 773 Classical Control of Modular Multilevel Converter 793.1 Introduction 793.2 Overview of Classical Control Method 803.3 Submodule Capacitor Voltage Control 823.3.1 Leg Voltage Control 823.3.2 Voltage Balance Strategy 833.4 Output Current Control 883.4.1 Reference Frame Theory 883.4.2 Control of MMC with Passive Load 923.5 Circulating Current Control 953.5.1 Mathematical Model 963.5.2 Control in Synchronous-dq Reference Frame 973.5.3 Control in Stationary-abc Reference Frame 1003.6 Summary 101References 1014 Model Predictive Control of Modular Multilevel Converter 1034.1 Introduction 1034.2 Mathematical Model of mmc 1054.2.1 Continuous-Time Model 1054.2.2 Discretization Methods 1084.2.3 Discrete-Time Model 1104.3 Extrapolation Techniques 1134.3.1 Vector Angle Extrapolation 1134.3.2 Lagrange Extrapolation 1134.4 Cost Function and Weight factors 1144.4.1 Formulation of Cost Function 1144.4.2 Selection of Weight Factors 1164.5 Direct Model Predictive Control 1174.5.1 Design Procedure 1174.5.2 Control Algorithm 1204.6 Indirect Model Predictive Control 1244.6.1 Design Procedure 1254.6.2 Control Algorithm 1274.7 Summary 128References 128Part II Advanced Modular Multilevel Converters5 Passive Cross-Connected Modular Multilevel Converters 1335.1 Introduction 1335.2 Passive Cross-Connected mmc 1345.2.1 Con guration of Power Circuit 1345.2.2 Switching States and Output Voltage 1355.3 Principle of Operation 1385.3.1 Modeling of PC-MMC 1385.3.2 Phase-Shifted Carrier Modulation for PC-MMC 1405.4 Low/Zero Frequency Operation of PC-MMC 1445.4.1 Equivalent Circuit 1455.4.2 Design of Cross-Connected Capacitor 1465.4.3 Submodule Capacitor Voltage Ripple 1485.4.4 Common-Mode Voltage 1515.5 Classical Control of PC-MMC 1535.5.1 Output Current Control 1545.5.2 Submodule Capacitor Voltage Control 1565.5.3 Synthesis of Modulation Signals 1595.6 Summary 162References 1626 Active Cross-Connected Modular Multilevel Converters 1656.1 Introduction 1656.2 Active Cross-Connected mmc 1666.2.1 Circuit Con guration of AC-MMC 1666.2.2 Switching States and Output Voltage 1666.3 Principles of Operation 1696.3.1 Modeling of AC-MMC 1706.3.2 Phase-Shifted Carrier Modulation for AC-MMC 1716.4 Low-Frequency Operation of AC-MMC 1766.4.1 Equivalent Circuit 1766.4.2 Submodule Capacitor Voltage Ripple 1786.4.3 Common-Mode Voltage 1816.4.4 Current Stress on Semiconductor Devices 1846.5 Classical Control of AC-MMC 1856.5.1 Output Current Control 1866.5.2 Submodule Capacitor Voltage Control 1866.5.3 Synthesis of Modulation Signals 1896.6 Summary 192References 1927 Star and Delta-Channel Modular Multilevel Converters 1957.1 Introduction 1957.2 Star-Channel Modular Multilevel Converter 1967.2.1 Circuit Con guration of Star-Channel mmc 1967.2.2 Switching States and Output Voltage 1977.3 Principles of Operation 2007.3.1 Modeling of Star-Channel mmc 2007.3.2 Phase-Shifted Carrier Modulation for Star-Channel mmc 2037.4 Low-Frequency Operation of Star-Channel mmc 2077.4.1 Equivalent Circuit 2087.4.2 Submodule Capacitor Voltage Ripple 2097.4.3 Common-Mode Voltage 2137.5 Classical Control of Star-Channel mmc 2167.5.1 Output Current Control 2177.5.2 Submodule Capacitor Voltage Control 2177.5.3 Synthesis of Modulation Signals 2217.6 Delta-Channel Modular Multilevel Converter 2237.7 Comparison of Advanced Modular Multilevel Converters 2257.8 Summary 226References 227Part III Applications of Modular Multilevel Converters8 Modular Multilevel Converter Based Medium-Voltage Motor Drives 2318.1 Introduction 2318.2 Fundamentals of MMC-Based Motor Drive 2328.2.1 System Con gurations 2328.2.2 Control Schemes 2338.3 Voltage-Oriented Control of Grid-Side mmc 2348.3.1 Principle of voltage orientation 2358.3.2 Implementation of PLL 2368.3.3 Block diagram of VOC 2378.4 Indirect Field-Oriented Control of Motor-side mmc 2408.4.1 Principle of Field Orientation 2418.4.2 Rotor Flux Vector Estimator 2428.4.3 Block diagram of IFOC approach 2448.5 Low-Speed Operation of MMC-based Motor Drive 2488.5.1 Analysis of Submodule Capacitor Voltage Ripple 2488.5.2 Analysis of MMC with High-Frequency Voltage and Current Injection 2548.5.3 Estimation of High-Frequency Voltage and Current Magnitude 2568.5.4 Minimization of Submodule Capacitor Voltage Ripple 2578.6 Common-Mode Voltage Issues and Blocking Schemes 2628.6.1 De nition of Common-Mode Voltage 2628.6.2 Blocking of Common-Mode Voltage 2648.7 Transformer-less MMC-based Motor Drive 2658.8 Summary 269References 2699 Role of Modular Multilevel Converters In The Power System 2719.1 Introduction 2719.2 MMC-Based HVDC Transmission Systems 2729.2.1 Two-Terminal System 2739.2.2 Multi-Terminal System 2749.2.3 DC-Side Short-Circuit Fault Protection 2759.2.4 HVDC Circuit Breakers 2779.3 Control of Two-Terminal MMC-Based HVDC System 2789.3.1 Sending-End Converter Control 2799.3.2 Receiving-End Converter Control 2819.4 Control of Multi-Terminal MMC-Based HVDC System 2869.4.1 Voltage Margin Control Scheme 2889.4.2 Voltage Droop Control Scheme 2939.5 MMC-based Static Synchronous Compensator 2949.5.1 System Con guration 2959.5.2 Reactive Power Compensation 2959.5.3 Compensation of Unbalanced AC-Grid Currents 2989.6 MMC-based Uni ed Power Quality Conditioner 3069.7 Summary 307References 307Appendix A MATLAB Demo Projects 311References 312Index 313