Contents Chapter 1 Overview of HVDC Transmission System 1 1.1 Overview of the Development of HVDC Transmission Technology.1 1.2 Technical Characteristics of HVDC Transmission 2 1.2.1 Advantages of HVDC Transmission 3 1.2.2 Disadvantages of HVDC Transmission 4 1.3 Structure of HVDC Transmission System.6 1.3.1 Two-Terminal HVDC Transmission 7 1.3.2 Monopolar DC Transmission 9 1.3.3 Bipolar System 11 1.3.4 Back-to-Back DC System 14 1.3.5 Multi-Terminal DC System 16 Chapter 2 Thyristor-Based Conversion and Configuration of Converter Station.20 2.1 Thyristor 20 2.1.1 Thyristor Structure 20 2.1.2 Dynamic Characteristics of Thyristor 21 2.1.3 Trigger of Thyristor 23 2.1.4 Thyristors in Series 24 2.2 Thyristor Commutation Technology 26 2.2.1 Line-Commutated Converters 26 2.2.2 Analysis of Six-Pulse Rectifier 27 2.2.3 Analysis of Six-Pulse Inverter 31 2.2.4 DC Voltage of Six-Pulse Converter 33 2.2.5 DC Voltage of Twelve-Pulse Converter40 2.3 Composition and Arrangement of Converter Station 45 2.4 Equipment in Converter Station.49 2.4.1 Converter Valve 49 2.4.2 Converter Transformer 52 2.4.3 Smoothing Reactor 56 2.4.4 AC Filter 59 2.4.5 DC Filter 61 2.4.6 Reactive Power Compensation 63 2.4.7 Other Equipments 65 2.5 Main Connection of Converter Station 66 2.5.1 Wiring of Converters 66 2.5.2 Connection Between the Converter Transformer and the Converter Valves 67 2.5.3 AC Filter Access System 69 2.5.4 DC Switchyard Wiring 71 2.6 Converter Control Mode and Configuration 73 2.6.1 Converter Control Mode73 2.6.2 Converter Control Configuration 76 2.6.3 Controller Model of Converter 81 Chapter 3 Operating Characteristics and Fault Analysis of DC System 88 3.1 Steady-State Operating Characteristics of DC System 88 3.1.1 Operating External Characteristics of DC System88 3.1.2 Power Characteristics of Converter 94 3.1.3 Harmonic Characteristics of Converter.101 3.2 Reactive Power Balance in DC System 110 3.3 Operation Mode of DC Transmission System 113 3.3.1 Operation Wiring Mode 114 3.3.2 Full-Voltage Operation and Reduced-Voltage Operation 119 3.3.3 Power Forward and Reverse Transmission Mode 120 3.3.4 Bipolar Symmetry and Asymmetry Operation Mode 120 3.4 Failure Analysis of DC Transmission System 124 3.4.1 Converter Failure 124 3.4.2 Fault on DC Side of Converter Station 136 3.4.3 Fault on AC Side of Converter Station.137 3.4.4 HVDC Line Fault and Grounding Electrode Fault 146 Chapter 4 Temporary and Switching Overvoltages in HVDC Converter Station 149 4.1 Overvoltage from AC Side of the Converter Station 149 4.1.1 Ground Fault on AC Side151 4.1.2 Clearing of Ground Fault on AC Side.154 4.1.3 Switching of Converter Transformer 157 4.1.4 Operating Lines on AC Side 161 4.1.5 Operating Filters at Converter Station 164 4.1.6 Overvoltage at Load Rejection 165 4.2 Overvoltage from DC Side of the Converter Station 167 4.2.1 Commissioning or Decommissioning of Twelve Pulse Converter 167 4.2.2 Short Circuit to Ground on Valve Side of Converter Transformer 168 4.2.3 Overvoltage Generated on the Converter Valve Bridge 174 4.2.4 Ground Fault on DC Side Line.176 4.3 Losing of AC Power on the Inverter Side 180 4.4 Commutation Failure 182 4.4.1 Analysis of Commutation Failure Process 182 4.4.2 Reactive Power Fluctuation Caused by Commutation Failure 185 4.4.3 Transient Overvoltage Characteristics Caused by Commutation Failure191 4.4.4 Influence of Control System Parameters on Overvoltage Caused by Commutation Failure 193 4.5 Fault on Neutral Bus204 4.6 Open Circuit Fault on Grounding Electrode Lead 206 Chapter 5 Lightning and Steep Front Overvoltage in HVDC Converter Station 208 5.1 Lightning Simulation.208 5.1.1 Types of Lightning Stroke 208 5.1.2 Lightning Current 209 5.1.3 Lightning Stroke Density and Point 212 5.2 Lightning Overvoltage on AC Side 212 5.2.1 Lightning Overvoltage due to Shielding Failure 213 5.2.2 Lightning Overvoltage of Return Stroke 214 5.2.3 Induced Lightning Overvoltage.218 5.2.4 Lightning Intrusive Surge.219 5.3 Shielding Failure in AC and DC Switchyards 220 5.4 Lightning Overvoltage on Line of DC Side 224 5.4.1 Computation Models224 5.4.2 Lightning Overvoltage of Shielding Failure on Line of DC Side.228 5.4.3 Return Stroke Overvoltage on Line on the DC Side 231 5.5 Steep Front Surge.234 5.5.1 Short Circuit or Flashover to Earth235 5.5.2 All Turned-on of Converter Valves and Mis-operation of Bypass Pair in Part of Converters.237 5.6 Simulation Model and Research Method of Overvoltage 238 5.6.1 System Simulation Model 238 5.6.2 Research Methods for Determination of Overvoltage 242 Chapter 6 Insulation Coordination Method for