Page 8 - Hybrid-Renewable Energy Systems in Microgrids

Contents vii

5 Multilevel Inverters for Photovoltaic Energy Systems in
Hybrid-Renewable Energy Systems 81
Ehsan Najafi, Natarajan Prabaharan
1 Multilevel Inverter Topology 81
1.1 Switching Sequences 84
1.2 Number of Components 87
2 Evolution of Hybrid Multilevel Inverters 88
3 Leakage Current in Photo Voltaic Inverters 92
References 96

6 An Overview of Control Techniques and Technical Challenge
for Inverters in Micro Grid 97
Natarajan Prabaharan, Amalorpavaraj Rini Ann Jerin, Ehsan Najafi,
Kaliannan Palanisamy
1 Introduction 97
2 Grid Inverter Synchronization 98
2.1 Highlights of PLL Techniques 99
3 Controllers Based on Inverter in Microgrids 101
3.1 Centralized Method 103
3.2 Decentralized Method 103
3.3 Hierarchical Control 103
4 Dynamic Security of Microgrids 104
4.1 Challenges in Microgrid 104
5 Conclusion 105
References 105

7 Study of Control Strategies of Power Electronics During Faults
in Microgrids 109
Jundi Jia, Guangya Yang, Arne Hejde Nielsen, Peter Rønne-Hansen
1 Introduction 109
2 Instantaneous Power Theory 110
3 Grid-Connected Mode 113
3.1 Flexible Oscillating Power Control 115
3.2 Flexible Positive- and Negative-Sequence Power Control 118
3.3 Inner Current Controller 121
3.4 Converter Current Limitation 126
4 Islanded Mode 131
4.1 Basic Control Structure 132
4.2 Negative-Sequence Component Control 135
5 Simulation Results 136
5.1 System Description 136
5.2 Steady State 137
5.3 Performance Under Unbalanced Faults 139
5.4 Discussion on Microgrid Protection 141
References 145