Preface

Renewable energy-based distributed power generation systems (RE-DPGS) represent promising solutions to mitigate energy crisis and environmental pollution. The LCL-type grid-connected inverter, being a conversion interface between the renewable energy power generation units and the power grid, has been widely used to convert dc power to high-quality ac power and feed it into the grid, and it plays an important role in maintaining safe, stable, and high-quality operation of RE-DPGS. This book aims to present the control techniques for the LCL-type grid-connected inverter to improve the system stability, control performance, and suppression of grid current harmonics. The detailed theoretical analysis with design examples and experimental validations are included. This book contains twelve chapters. Chapter 1 gives a brief review of the key techniques for the LCL-type grid-connected inverter, including the design and magnetic integration of the LCL filter, design of the controller parameters, the control delay effects in digital control and the methods of reducing the control delays, suppression of the grid current distortion caused by the grid voltage harmonics, and the grid impedance effects on the system stability and the methods to improve the system stability. Chapter 2 introduces the modulation strategies for the single-phase and three-phase inverters, and presents the design methods of LCL filters for both single-phase and three-phase inverters. Chapter 3 presents magnetic integration methods for LCL filters, aiming to reduce volume and weight. In Chap. 4, the resonance hazard of LCL filters is analyzed, and six basic passive-damping solutions are discussed in terms of their effects on the characteristics of LCL filters. It is pointed out that adding a resistor in parallel with the filter capacitor can effectively damp the resonance peak and does not affect the frequency response of the LCL filter, but it results in high power loss. The