Offshore Wind Energy Generation : Control, Protection, and Integration to Electrical Systems

[Book Description]

The offshore wind sector's trend towards larger turbines, bigger wind farm projects and greater distance to shore has a critical impact on grid connection requirements for offshore wind power plants. This important reference sets out the fundamentals and latest innovations in electrical systems and control strategies deployed in offshore electricity grids for wind power integration.Includes: * All current and emerging technologies for offshore wind integration and trends in energy storage systems, fault limiters, superconducting cables and gas-insulated transformers * Protection of offshore wind farms illustrating numerous system integration and protection challenges through case studies * Modelling of doubly-fed induction generators (DFIG) and full-converter wind turbines structures together with an explanation of the smart grid concept in the context of wind farms * Comprehensive material on power electronic equipment employed in wind turbines with emphasis on enabling technologies (HVDC, STATCOM) to facilitate the connection and compensation of large-scale onshore and offshore wind farms * Worked examples and case studies to help understand the dynamic interaction between HVDC links and offshore wind generation * Concise description of the voltage source converter topologies, control and operation for offshore wind farm applications * Companion website containing simulation models of the cases discussed throughout Equipping electrical engineers for the engineering challenges in utility-scale offshore wind farms, this is an essential resource for power system and connection code designers and pratitioners dealing with integation of wind generation and the modelling and control of wind turbines.It will also provide high-level support to academic researchers and advanced students in power and renewable energy as well as technical and research staff in transmission and distribution system operators and in wind turbine and electrical equipment manufacturers.

[Table of Contents]

 

 

Preface                                            xi
About the Authors                                  xiii
Acronyms and Symbols                               xv
1 Offshore Wind Energy Systems                     1   (14)
  1.1 Background                                   1   (1)
  1.2 Typical Subsystems                           1   (3)
  1.3 Wind Turbine Technology                      4   (4)
    1.3.1 Basics                                   4   (2)
    1.3.2 Architectures                            6   (1)
    1.3.3 Offshore Wind Turbine Technology         7   (1)
    Status
  1.4 Offshore Transmission Networks               8   (1)
  1.5 Impact on Power System Operation             9   (3)
    1.5.1 Power System Dynamics and Stability      10  (1)
    1.5.2 Reactive Power and Voltage Support       10  (1)
    1.5.3 Frequency Support                        11  (1)
    1.5.4 Wind Turbine Inertial Response           11  (1)
  1.6 Grid Code Regulations for the Connection     12  (1)
  of Wind Generation
  Acknowledgements                                 13  (1)
  References                                       14  (1)
2 DFIG Wind Turbine                                15  (58)
  2.1 Introduction                                 15  (2)
    2.1.1 Induction Generator (IG)                 15  (1)
    2.1.2 Back-to-Back Converter                   16  (1)
    2.1.3 Gearbox                                  16  (1)
    2.1.4 Crowbar Protection                       16  (1)
    2.1.5 Turbine Transformer                      17  (1)
  2.2 DFIG Architecture and Mathematical           17  (19)
  Modelling
    2.2.1 IG in the abc Reference Frame            17  (6)
    2.2.2 IG in the dq0 Reference Frame            23  (4)
    2.2.3 Mechanical System                        27  (2)
    2.2.4 Crowbar Protection                       29  (1)
    2.2.5 Modelling of the DFIG B2B Power          30  (3)
    Converter
    2.2.6 Average Modelling of Power Electronic    33  (2)
    Converters
    2.2.7 The dc Circuit                           35  (1)
  2.3 Control of the DFIG WT                       36  (11)
    2.3.1 PI Control of Rotor Speed                36  (3)
    2.3.2 PI Control of DFIG Reactive Power        39  (2)
    2.3.3 PI Control of Rotor Currents             41  (1)
    2.3.4 PI Control of dc Voltage                 42  (3)
    2.3.5 PI Control of Grid-side Converter        45  (2)
    Currents
  2.4 DFIG Dynamic Performance Assessment          47  (13)
    2.4.1 Three-phase Fault                        47  (4)
    2.4.2 Symmetrical Voltage Dips                 51  (2)
    2.4.3 Asymmetrical Faults                      53  (1)
    2.4.4 Single-Phase-to-Ground Fault             54  (1)
    2.4.5 Phase-to-Phase Fault                     55  (1)
    2.4.6 Torque Behaviour under Symmetrical       56  (2)
    Faults
    2.4.7 Torque Behaviour under Asymmetrical      58  (1)
    Faults
    2.4.8 Effects of Faults in the Reactive        59  (1)
    Power Consumption of the IG
  2.5 Fault Ride-Through Capabilities and Grid     60  (2)
  Code Compliance
    2.5.1 Advantages and Disadvantages of the      60  (1)
    Crowbar Protection
    2.5.2 Effects of DFIG Variables over Its       61  (1)
    Fault Ride-Through Capabilities
  2.6 Enhanced Control Strategies to Improve       62  (10)
  DFIG Fault Ride-Through Capabilities
    2.6.1 The Two Degrees of Freedom Internal      62  (3)
    Model Control (IMC)
    2.6.2 IMC Controller of the Rotor Speed        65  (1)
    2.6.3 IMC Controller of the Rotor Currents     66  (1)
    2.6.4 IMC Controller of the dc Voltage         67  (2)
    2.6.5 IMC Controller of the Grid-Side          69  (1)
    Converter Currents
    2.6.6 DFIG IMC Controllers Tuning for          70  (1)
    Attaining Robust Control
    2.6.7 The Robust Stability Theorem             70  (2)
  References                                       72  (1)
3 Fully-Rated Converter Wind Turbine (FRC-WT)      73  (40)
  3.1 Synchronous Machine Fundamentals             73  (6)
    3.1.1 Synchronous Generator Construction       73  (1)
    3.1.2 The Air-Gap Magnetic Field of the        74  (5)
    Synchronous Generator
  3.2 Synchronous Generator Modelling in the dq    79  (6)
  Frame
    3.2.1 Steady-State Operation                   81  (1)
    3.2.2 Synchronous Generator with Damper        82  (3)
    Windings
  3.3 Control of Large Synchronous Generators      85  (3)
    3.3.1 Excitation Control                       86  (1)
    3.3.2 Prime Mover Control                      87  (1)
  3.4 Fully-Rated Converter Wind Turbines          88  (1)
  3.5 FRC-WT with Synchronous Generator            89  (11)
    3.5.1 Permanent Magnets Synchronous            90  (2)
    Generator
    3.5.2 FRC-WT Based on Permanent Magnet         92  (1)
    Synchronous Generator
    3.5.3 Generator-Side Converter Control         93  (3)
    3.5.4 Modelling of the dc Link                 96  (2)
    3.5.5 Network-Side Converter Control           98  (2)
  3.6 FRC-WT with Squirrel-Cage Induction          100 (5)
  Generator
    3.6.1 Control of the FRC-IG Wind Turbine       100 (5)
  3.7 FRC-WT Power System Damper                   105 (5)
    3.7.1 Power System Oscillations Damping        105 (2)
    Controller
    3.7.2 Influence of Wind Generation on          107 (1)
    Network Damping
    3.7.3 Influence of FRC-WT Damping              108 (2)
    Controller on Network Damping
  Acknowledgements                                 110 (2)
  References                                       112 (1)
4 Offshore Wind Farm Electrical Systems            113 (42)
  4.1 Typical Components                           113 (1)
  4.2 Wind Turbines for Offshore ? General         113 (2)
  Aspects
  4.3 Electrical Collectors                        115 (3)
    4.3.1 Wind Farm Clusters                       118 (1)
  4.4 Offshore Transmission                        118 (23)
    4.4.1 HVAC Transmission                        118 (2)
    4.4.2 HVDC Transmission                        120 (2)
    4.4.3 CSC-HVDC Transmission                    122 (6)
    4.4.4 VSC-HVDC Transmission                    128 (12)
    4.4.5 Multi-Terminal VSC-HVDC Networks         140 (1)
  4.5 Offshore Substations                         141 (3)
  4.6 Reactive Power Compensation Equipment        144 (6)
    4.6.1 Static Var Compensator (SVC)             144 (3)
    4.6.2 Static Compensator (STATCOM)             147 (3)
  4.7 Subsea Cables                                150 (1)
    4.7.1 Ac Subsea Cables                         150 (1)
    4.7.2 Dc Subsea Cables                         150 (1)
    4.7.3 Modelling of Underground and Subsea      150 (1)
    Cables
  Acknowledgements                                 151 (1)
  References                                       151 (4)
5 Grid Integration of Offshore Wind Farms ?        155 (18)
Case Studies
  5.1 Background                                   155 (1)
  5.2 Offshore Wind Farm Connection Using          156 (3)
  Point-to-Point VSC-HVDC Transmission
  5.3 Offshore Wind Farm Connection Using HVAC     159 (2)
  Transmission
  5.4 Offshore Wind Farm Connected Using           161 (3)
  Parallel HVACNSC-HVDC Transmission
  5.5 Offshore Wind Farms Connected Using a        164 (4)
  Multi-Terminal VSC-HVDC Network
  5.6 Multi-Terminal VSC-HVDC for Connection of    168 (3)
  Inter-Regional Power Systems
  Acknowledgements                                 171 (1)
  References                                       171 (2)
6 Offshore Wind Farm Protection                    173 (20)
  6.1 Protection within the Wind Farm ac Network   173 (7)
    6.1.1 Wind Generator Protection Zone           174 (4)
    6.1.2 Feeder Protection Zone                   178 (1)
    6.1.3 Busbar Protection Zone                   179 (1)
    6.1.4 High-Voltage Transformer Protection      180 (1)
    Zone
  6.2 Study of Faults in the ac Transmission       180 (4)
  Line of an Offshore DFIG Wind Farm
    6.2.1 Case Study 1                             181 (1)
    6.2.2 Case Study 2                             181 (3)
  6.3 Protections for dc Connected Offshore        184 (8)
  Wind Farms
    6.3.1 VSC-HVDC Converter Protection Scheme     184 (1)
    6.3.2 Analysis of dc Transmission Line Fault   185 (1)
    6.3.3 Pole-to-Pole Faults                      186 (1)
    6.3.4 Pole-to-Earth Fault                      187 (1)
    6.3.5 HVDC dc Protections: Challenges and      188 (1)
    Trends
    6.3.6 Simulation Studies of Faults in the      188 (4)
    dc Transmission Line of an Offshore DFIG
    Wind Farm
  Acknowledgements                                 192 (1)
  References                                       192 (1)
7 Emerging Technologies for Offshore Wind          193 (30)
Integration
  7.1 Wind Turbine Advanced Control for Load       193 (2)
  Mitigation
    7.1.1 Blade Pitch Control                      193 (1)
    7.1.2 Blade Twist Control                      194 (1)
    7.1.3 Variable Diameter Rotor                  194 (1)
    7.1.4 Active Flow Control                      195 (1)
  7.2 Converter Interface Arrangements and         195 (8)
  Collector Design
    7.2.1 Converters on Turbine                    195 (3)
    7.2.2 Converters on Platform                   198 (2)
    7.2.3 Ac Collection Options: Fixed or          200 (2)
    Variable Frequency
    7.2.4 Evaluation of >Higher (>33 kV)           202 (1)
    Collection Voltage
  7.3 Dc Transmission Protection                   203 (1)
  7.4 Energy Storage Systems (EESs)                204 (3)
    7.4.1 Batteries                                205 (1)
    7.4.2 Super-Capacitors                         205 (1)
    7.4.3 Flywheel Storage System                  205 (1)
    7.4.4 Pumped-Hydro Storage                     206 (1)
    7.4.5 Compressed-Air Storage Systems           206 (1)
    7.4.6 Superconducting Magnetic Energy          206 (1)
    Storage (SMES)
  7.5 Fault Current Limiters (FCLs)                207 (1)
  7.6 Sub-Sea Substations                          207 (1)
  7.7 HTSCs, GITs and GILs                         208 (1)
    7.7.1 HTSCs (High-Temperature                  208 (1)
    Superconducting Cables)
    7.7.2 GITs (Gas-Insulated Transformers)        208 (1)
    7.7.3 GILs (Gas-Insulated Lines)               209 (1)
  7.8 Developments in Condition Monitoring         209 (4)
    7.8.1 Partial Discharge Monitoring in HV       209 (1)
    Cables
    7.8.2 Transformer Condition Monitoring         210 (1)
    7.8.3 Gas-Insulated Switchgear Condition       211 (1)
    Monitoring
    7.8.4 Power Electronics Condition Monitoring   211 (2)
  7.9 Smart Grids for Large-Scale Offshore Wind    213 (4)
  Integration
    7.9.1 VPP Control Approach                     216 (1)
    7.9.2 Phasor Measurement Units                 217 (1)
  Acknowledgements                                 217 (1)
  References                                       218 (5)
Appendix A Voltage Source Converter Topologies     223 (48)
  A.1 Two-Level Converter                          223 (17)
    A.1.1 Operation                                223 (1)
    A.1.2 Voltage Source Converter Square-Mode     224 (1)
    Operation
    A.1.3 Pulse Width Modulation                   225 (15)
  A.2 Neutral-Point Clamped Converter              240 (7)
    A.2.1 Selective Harmonic Elimination           242 (2)
    A.2.2 Sinusoidal Pulse Width Modulation        244 (3)
  A.3 Flying Capacitor (FC) Multilevel Converter   247 (1)
  A.4 Cascaded Multilevel Converter                248 (1)
  A.5 Modular Multilevel Converter                 249 (9)
  References                                       258 (13)
Appendix B Worked-out Examples                     271 (8)
Index                                              279