Control and Filter Design of Single-Phase Grid-Connected Converters

Weimin Wu is a Professor in the Department of Electrical Engineering at the Shanghai Maritime University in China. Frede Blaabjerg is a Professor in the Department of Energy at Aalborg University in Denmark. Henry Chung is Chair Professor of Electrical Engineering at City University of Hong Kong, China. Yuanbin He is Associate Professor in the School of Automation at Hangzhou Dianzi University in China. Min Huang is a Lecturer in the Department of Electrical Engineering at the Shanghai Maritime University in China.

Author Biography xiii Preface xvii Part I Background 1 1 Introduction 3 1.1 Architecture of DG Grid-Connected Converter 3 1.1.1 Power Conversion Stage 5 1.1.1.1 Switching Network 5 1.1.1.2 Output Filter 6 1.1.2 Control Stage 7 1.2 Challenges for Controlling DG Grid-Connected VSCs with High-Order Power Filter 8 1.2.1 Intrinsic Challenges 8 1.2.1.1 Filter Parametric Sensitivities 9 1.2.1.2 Digital Delay 10 1.2.2 Extrinsic Challenges 10 1.2.2.1 Grid Impedance Variation 10 1.2.2.2 Disturbances at the PCC 10 1.3 Methods for Controlling DG Grid-Connected VSCs with High-Order Power Filter 12 1.3.1 Methodologies to Assess the Stability of DG Grid-Connected VSCs 12 1.3.1.1 Eigenvalue-Based Analysis 12 1.3.1.2 Impedance-Based Stability Analysis 12 1.3.1.3 Application Issue Related to Impedance-Based Stability Analysis 13 1.3.2 Methods to Mitigate Filter Resonance 14 1.3.2.1 Online Grid Impedance Estimation 14 1.3.2.2 Inherent Damping 15 1.3.2.3 Passive Damping 15 1.3.2.4 Active Damping 17 1.3.2.5 Hybrid Damping 19 1.3.3 Harmonic distortion Mitigation Methods 20 1.4 Supplementary Note 21 References 22 2 Control Structure and Modulation Techniques of Single-Phase Grid-Connected Inverter 29 2.1 Control Structure of Single-Phase Grid-Connected Inverter 29 2.1.1 Natural Frame Control 30 2.1.2 Synchronous Reference Frame Control 32 2.1.3 Grid Synchronization Methods 33 2.1.3.1 Zero-Crossing Method 33 2.1.3.2 Filtering of Grid Voltages 34 2.1.3.3 PLL Technique 34 2.2 Modulation Methods 35 2.2.1 Unipolar Modulation Method 35 2.2.1.1 Continuous Unipolar Modulation 36 2.2.1.2 Discontinuous Unipolar Modulation 36 2.2.2 Bipolar Modulation Method 39 2.3 Summary 40 References 41 Part II LCL/LLCL Power Filter 43 3 An LLCL Power Filter for Single-Phase Grid-Connected Inverter 45 3.1 Introduction 45 3.2 Principle of Traditional LCL Filter and Proposed LLCL Filter 46 3.3 Parametric Design of LCL and LLCL Filters 49 3.3.1 Constraints and Procedure of Power Filter Design 49 3.3.2 Saving Analysis on the Grid-Side Inductance 53 3.3.3 Specific Design Consideration for a Simple Passive Damping Strategy 53 3.4 Design Examples for LCL and LLCL filters 54 3.5 Experimental Results 56 3.5.1 Experimental Results 57 3.5.2 Analysis and Discussion 58 3.6 Summary 59 References 59 4 Modeling and Suppressing Conducted Electromagnetic Interference Noise for LCL/LLCL-Filtered Single-Phase Transformerless Grid-Connected Inverter 61 4.1 Introduction 61 4.2 Conducted EMI Noise Analysis 62 4.2.1 CM and DM Voltage Noises 62 4.2.2 Spectrum of DM and CM Voltage Noise for GCI Using DUPWM 64 4.2.3 Spectrum of DM Voltage Noise for GCI Using BPWM 67 4.3 Modified LLCL Filter to Fully Suppress the Conducted EMI Noise for GCI Using DUPWM 68 4.3.1 Modified Solution for LLCL Filter 68 4.3.2 Improved Parameter Design of LLCL filter 72 4.3.3 Constraints on Harmonics of the Grid-Injected Current and EMI Noise Within 150 kHz to 1 MHz 72 4.3.3.1 Constraints on Leakage Current 73 4.3.4 Experimental Verification 74 4.3.4.1 Power Spectrum of the Grid-Injected Current 75 4.3.4.2 Measured Conducted EMI Noise 75 4.3.5 Negative Dc-rail Voltage with Respect to the Earth V Dc_n and Leakage Current 78 4.4 Novel DM EMI Suppressor for LLCL-Filtered GCI without CM Noise Issue 79 4.4.1 Proposed DM EMI Suppressor 79 4.4.2 Experimental Verification 83 4.5 Summary 85 4.5.1 For Single-Phase Transformerless GCI Using DUPWM 85 4.5.2 For Single-Phase Transformerless GCI Using BPWM or a System Without cm EMI Noise Issue 85 References 86 Part III Passive Damping 89 5 Design of Passive Damper for LCL/LLCL-Filtered Grid-Connected Inverter 91 5.1 Introduction 91 5.2 Design Method for Passive Damping 92 5.2.1 Passive Damping Scheme of LCL Filter 92 5.2.2 Passive Damping Scheme of LLCL Filter 95 5.2.3 Design Example 97 5.3 Analysis of Power Loss Cau