Cover

Title Page

Copyright

Contents

About the Authors

Preface

Acknowledgments

Chapter 1 Introduction

1.1 Modes of Operation of Microgrid Converters

1.1.1 Grid Connection Mode

1.1.2 Stand-Alone Mode

1.1.3 Battery Charging Mode

1.2 Converter Topologies

1.3 Modulation Strategies

1.4 Control and System Issues

1.5 Future Challenges and Solutions

References

Chapter 2 Converter Topologies

2.1 Topologies

2.1.1 The Two-Level Converter

2.1.2 The NPC Converter

2.1.3 The CHB Converter

2.2 Pulse Width Modulation Strategies

2.2.1 Carrier-Based Strategies

2.2.2 SVM Strategies

2.3 Modeling

References

Chapter 3 DC-Link Capacitor Current and Sizing in NPC and CHB Inverters

3.1 Introduction

3.2 Inverter DC-Link Capacitor Sizing

3.3 Analytical Derivation of DC-Link Capacitor Current RMS Expressions

3.3.1 NPC Inverter

3.3.2 CHB Inverter

3.4 Analytical Derivation of DC-Link Capacitor Current Harmonics

3.4.1 NPC Inverter

3.4.2 CHB Inverter

3.5 Numerical Derivation of DC-Link Capacitor Current RMS Value and Voltage Ripple Amplitude

3.6 Simulation Results

3.7 Discussion

3.7.1 Comparison of Capacitor Size for the NPC and CHB Inverters

3.7.2 Comparison of Presented Methods for Analyzing DC-Link Capacitor Current

3.7.3 Extension to Higher-Level Inverters

3.8 Conclusion

References

Chapter 4 Loss Comparison of Two- and Three-Level Inverter Topologies

4.1 Introduction

4.2 Selection of IGBT-Diode Modules

4.3 Switching Losses

4.3.1 Switching Losses in the Two-Level Inverters

4.3.2 Switching Losses in the NPC Inverter

4.3.3 Switching Losses in the CHB Inverter

4.4 Conduction Losses

4.4.1 Conduction Losses in the Two-Level Inverter

4.4.2 Conduction Losses in the NPC Inverter

4.4.3 Conduction Losses in the CHB Inverter

4.5 DC-Link Capacitor RMS Current

4.6 Results

4.7 Conclusion

References

Chapter 5 Minimization of Low-Frequency Neutral-Point Voltage Oscillations in NPC Converters

5.1 Introduction

5.2 NPC Converter Modulation Strategies

5.3 Minimum NP Ripple Achievable by NV Strategies

5.3.1 Locally Averaged NP Current

5.3.2 Effect of Switching Constraints

5.3.3 Zero-Ripple Region

5.3.4 A Lower Boundary for the NP Voltage Ripple

5.4 Proposed Band-NV Strategies

5.4.1 Criterion Used by Conventional NV Strategies

5.4.2 Proposed Criterion

5.4.3 Regions of Operation

5.4.4 Algorithm

5.4.5 Switching Sequences – Conversion to Band-NV

5.5 Performance of Band-NV Strategies

5.5.1 NP Voltage Ripple

5.5.2 Effective Switching Frequency – Output Voltage Harmonic Distortion

5.6 Simulation of Band-NV Strategies

5.7 Hybrid Modulation Strategies

5.7.1 Proposed Hybrid Strategies

5.7.2 Simulation Results

5.8 Conclusions

References

Chapter 6 Digital Control of a Three-Phase Two-Level Grid-Connected Inverter

6.1 Introduction

6.2 Control Strategy

6.3 Digital Sampling Strategy

6.4 Effect of Time Delay on Stability

6.5 Capacitor Current Observer

6.6 Design of Feedback Controllers

6.7 Simulation Results

6.8 Experimental Results

6.9 Conclusions

References

Chapter 7 Design and Control of a Grid-Connected Interleaved Inverter

7.1 Introduction

7.2 Ripple Cancellation

7.3 Hardware Design

7.3.1 Hardware Design Guidelines

7.3.2 Application of the Design Guidelines

7.4 Controller Structure

7.5 System Analysis

7.5.1 Effect of Passive Damping and Grid Impedance

7.5.2 Effect of Computational Time Delay

7.5.3 Grid Disturbance Rejection

7.6 Controller Design

7.7 Simulation and Practical Results

7.8 Conclusions

References

Chapter 8 Repetitive Current Control of an Interleaved Grid-Connected Inverter

8.1 Introduction

8.2 Proposed Controller and System Modeling

8.3 System Analysis and Controller Design

8.4 Simulation Results

8.5 Experimental Results

8.6 Conclusions

References

Chapter 9 Line Interactive UPS

9.1 Introduction

9.2 System Overview

9.3 Core Controller

9.3.1 Virtual Impedance and Grid Harmonics Rejection

9.4 Power Flow Controller

9.4.1 Drooping Control Equations

9.4.2 Small Signal Analysis

9.4.3 Stability Analysis and Drooping Coefficients Selection

9.5 DC Link Voltage Controller

9.6 Experimental Results

9.7 Conclusions

References

Chapter 10 Microgrid Protection

10.1 Introduction

10.2 Key Protection Challenges

10.2.1 Fault Current Level Modification

10.2.2 Device Discrimination

10.2.3 Reduction in Reach of Impedance Relays

10.2.4 Bidirectionality and Voltage Profile Change

10.2.5 Sympathetic Tripping

10.2.6 Islanding

10.2.7 Effect on Feeder Reclosure

10.3 Possible Solutions to Key Protection Challenges

10.3.1 Possible Solutions to Key Protection Challenges for an Islanded Microgrid Having IIDG Units

10.4 Case Study

10.4.1 Fault Level Modification

10.4.2 Blinding of Protection

10.4.3 Sympathetic Tripping

10.4.4 Reduction in Reach of Distance Relay

10.4.5 Discussion

10.5 Conclusions

References

Chapter 11 An Adaptive Relaying Scheme for Fuse Saving

11.1 Introduction

11.1.1 Preventive Solutions Proposed in the Literature

11.1.2 Remedial Solutions Proposed in the Literature

11.1.3 Contributions of the Chapter

11.2 Case Study

11.3 Simulation Results and Discussion

11.4 Fuse Saving Strategy

11.4.1 Options and Considerations for the Selection of Ipickup of the 50 Element

11.4.2 Adaptive Algorithm

11.5 How Reclosing Will Be Applied

11.6 Observations

11.7 Conclusions

References

Appendix A SVM for the NPC Converter–MATLAB®-Simulink Models

A.1 Calculation of Duty Cycles for Nearest Space Vectors

A.2 Symmetric Modulation Strategy

A.3 MATLAB®-Simulink Models

References

Appendix B DC-Link Capacitor Current Numerical Calculation

Index