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

Description

Cover Title Page Copyright Page Contents Author Biography Preface Part I Background Chapter 1 Introduction 1.1 Architecture of DG Grid-Connected Converter 1.1.1 Power Conversion Stage 1.1.1.1 Switching Network 1.1.1.2 Output Filter 1.1.2 Control Stage 1.2 Challenges for Controlling DG Grid-Connected VSCs with High-Order Power Filter 1.2.1 Intrinsic Challenges 1.2.1.1 Filter Parametric Sensitivities 1.2.1.2 Digital Delay 1.2.2 Extrinsic Challenges 1.2.2.1 Grid Impedance Variation 1.2.2.2 Disturbances at the PCC 1.3 Methods for Controlling DG Grid-Connected VSCs with High-Order Power Filter 1.3.1 Methodologies to Assess the Stability of DG Grid-Connected VSCs 1.3.1.1 Eigenvalue-Based Analysis 1.3.1.2 Impedance-Based Stability Analysis 1.3.1.3 Application Issue Related to Impedance-Based Stability Analysis 1.3.2 Methods to Mitigate Filter Resonance 1.3.2.1 Online Grid Impedance Estimation 1.3.2.2 Inherent Damping 1.3.2.3 Passive Damping 1.3.2.4 Active Damping 1.3.2.5 Hybrid Damping 1.3.3 Harmonic distortion Mitigation Methods 1.4 Supplementary Note References Chapter 2 Control Structure and Modulation Techniques of Single-Phase Grid-Connected Inverter 2.1 Control Structure of Single-Phase Grid-Connected Inverter 2.1.1 Natural Frame Control 2.1.2 Synchronous Reference Frame Control 2.1.3 Grid Synchronization Methods 2.1.3.1 Zero-Crossing Method 2.1.3.2 Filtering of Grid Voltages 2.1.3.3 PLL Technique 2.2 Modulation Methods 2.2.1 Unipolar Modulation Method 2.2.1.1 Continuous Unipolar Modulation 2.2.1.2 Discontinuous Unipolar Modulation 2.2.2 Bipolar Modulation Method 2.3 Summary References Part II LCL/LLCL Power Filter Chapter 3 An LLCL Power Filter for Single-Phase Grid-Connected Inverter 3.1 Introduction 3.2 Principle of Traditional LCL Filter and Proposed LLCL Filter 3.3 Parametric Design of LCL and LLCL Filters 3.3.1 Constraints and Procedure of Power Filter Design 3.3.2 Saving Analysis on the Grid-Side Inductance 3.3.3 Specific Design Consideration for a Simple Passive Damping Strategy 3.4 Design Examples for LCL and LLCL filters 3.5 Experimental Results 3.5.1 Experimental Results 3.5.2 Analysis and Discussion 3.6 Summary References Chapter 4 Modeling and Suppressing Conducted Electromagnetic Interference Noise for LCL/LLCL-Filtered Single-Phase Transformerless Grid-Connected Inverter 4.1 Introduction 4.2 Conducted EMI Noise Analysis 4.2.1 CM and DM Voltage Noises 4.2.2 Spectrum of DM and CM Voltage Noise for GCI Using DUPWM 4.2.3 Spectrum of DM Voltage Noise for GCI Using BPWM 4.3 Modified LLCL Filter to Fully Suppress the Conducted EMI Noise for GCI Using DUPWM 4.3.1 Modified Solution for LLCL Filter 4.3.2 Improved Parameter Design of LLCL filter 4.3.3 Constraints on Harmonics of the Grid-Injected Current and EMI Noise Within 150 kHz to 1 MHz 4.3.3.1 Constraints on Leakage Current 4.3.4 Experimental Verification 4.3.4.1 Power Spectrum of the Grid-Injected Current 4.3.4.2 Measured Conducted EMI Noise 4.3.5 Negative DC-Rail Voltage with Respect to the Earth vdc_N and Leakage Current 4.4 Novel DM EMI Suppressor for LLCL-Filtered GCI without CM Noise Issue 4.4.1 Proposed DM EMI Suppressor 4.4.2 Experimental Verification 4.5 Summary 4.5.1 For Single-Phase Transformerless GCI Using DUPWM 4.5.2 For Single-Phase Transformerless GCI Using BPWM or a System Without CM EMI Noise Issue References Part III Passive Damping Chapter 5 Design of Passive Damper for LCL/LLCL-Filtered Grid-Connected Inverter 5.1 Introduction 5.2 Design Method for Passive Damping 5.2.1 Passive Damping Scheme of LCL Filter 5.2.2 Passive Damping Scheme of LLCL Filter 5.2.3 Design Example 5.3 Analysis of Power Loss Caused by the Filter 5.3.1 Passive Damping Power Loss 5.3.2 Power Losses in Inductors 5.4 Experimental Results 5.5 Summary References Chapter 6 Composite Passive Damping Scheme for LLCL-Filtered Grid-Connected Inverter 6.1 Introduction 6.2 Upper and Lower Limits of the PR + HC Controller Gain 6.2.1 LLCL Filter-Based Grid-Connected Inverter Configuration 6.2.2 Lower Limit of the PR + HC Controller Gain 6.2.3 Upper Limit of the PR + HC Controller Gain 6.3 E-Q-Factor-Based Passive Damping Design 6.3.1 Principle of the Equivalent Q-Factor Method 6.3.2 E-Q-Factor-Based RC Parallel Damping Design 6.3.3 E-Q-Factor-Based RL Series Damping Design 6.4 New Composite Passive Damping Scheme for the LLCL Filter 6.4.1 Composite Passive Damping Scheme 6.4.2 Design Example 6.4.3 Analysis of Achieved Damping 6.5 Experimental Verification 6.6 Summary References Part IV Robust Control Design Chapter 7 Robust Hybrid Damper Design for LCL/LLCL-Filtered Grid-Connected Inverter 7.1 Introduction 7.2 Control Bandwidth Analysis of the Grid-Current Feedback Method 7.2.1 LCL/LLCL-Filtered Grid-Connected Inverter System 7.2.2 Maximum Achieved Bandwidth of the Control Method 7.3 Proposed Single-Loop Control with High Bandwidth 7.3.1 Mathematical Model of the Proposed Single-Loop Control with Hybrid Damper 7.3.2 System-Characteristics-Based Single-Loop Control Design Methodology Step 1: Design of the RC Parallel Damper Step 2: Design of the Proportionality Coefficient Kp of the PR + HC Regulator Step 3: Determination of the Critical Grid Inductance Step 4: Determination of the Critical Frequency Region for Case 1 and the Critical Frequency (f0 of Case 1 and fL0 of Case 2) Step 5: Design of the Digital Notch Filter Step 6: Checking the Phase Margin of the Entire System 7.4 Design Example 7.4.1 System Design 7.4.2 System Parameter Robustness Analysis 7.5 Experimental Verification 7.6 Summary References Chapter 8 Robust Impedance-Based Design of LLCL-Filtered Grid-Connected Inverter against the Wide Variation of Grid Reactance 8.1 Introduction 8.2 Modeling of the LLCL-Type Grid-Connected Inverter 8.2.1 System Description 8.2.2 Norton Equivalent Model 8.3 Stability Analysis Considering Grid-Reactance Variation 8.3.1 Non-Passive Regions of Inverter Output Admittance 8.3.2 Possible Instability Under the Wide Variation of Grid Reactance 8.4 Proposed Measures and Design Procedure Under the Grid-Reactance Variation Condition 8.4.1 Proposed Measures Against Grid-Reactance Variation 8.4.2 Design Procedure Step 1- Calculate the Minimum Grid Inductance Lg_min Step 2- Design L1, Ctotal, and L2 Step 3- Design the Bypass Filtering Branch Step 4- Design the Minimum Grid Capacitance Cg_min Step 5- Design the Proportional Gain KP of the PR+HC Regulator Step 6- Select CEMI, Cd, and Rd Step 7- Check fi < fd2 8.5 Design Example 8.6 Simulation and Experimental Verification 8.6.1 Simulation 8.6.2 Experiments 8.6.2.1 Experimental Results 8.6.2.2 Analysis and Discussion 8.7 Summary References Part V Active Damping Chapter 9 Active Damping of LLCL-Filter Resonance Based on LC-Trap Voltage or Current Feedback 9.1 Introduction 9.2 Control of LLCL-Filtered Grid Converter 9.2.1 Description and General Control 9.2.2 Block Diagrams of Different Active Dampers 9.2.3 Effects of Delay Gd(s) 9.3 Circuit Equivalences of LLCL Active Dampers 9.3.1 General Virtual Impedance Model 9.3.2 LC-Trap Voltage Feedback 9.3.3 LC-Trap Current Feedback 9.4 Z-Domain Root-Locus Analysis 9.4.1 Z-Domain Transfer Functions 9.4.2 Root-Locus Analyses with Different Active Dampers 9.4.3 Comparison 9.5 Experimental Verification 9.6 Summary References Chapter 10 Enhancement of System Stability Using Active Cancelation to Eliminate the Effect of Grid Impedance on System Stability and Injected Power Quality of Grid-Connected Inverter 10.1 Introduction 10.2 Principle of the Grid Impedance Cancelator 10.3 Modeling with the Grid Impedance Cancelator 10.3.1 System Configuration with the Grid Impedance Cancelator 10.3.2 AC Voltage Regulation 10.3.3 Active Damping Function 10.3.4 DC Capacitor Voltage Control 10.4 Modeling of the Grid Impedance Cancelator 10.5 Experimental Verification 10.6 Summary References Index EULA