Analysis and Control of Single-Phase Grid-Connected Inverter with Inductive- Capacitive-Inductive Filter

Abstract

Owing to the increased penetration of a distributed generation system, a single-phase grid-connected inverter (SPGCI) with inductive-capacitive-inductive (LCL) filter has been widely used in a small-scale power generation system. However, for a grid-connected inverter-based generation system, power quality is affected by the resonance problem caused by LCL filter, and a control strategy is required. To enhance the power quality in a generation system that has SPGGI with an LCL filter, a dedicated control scheme based on grid voltage feedforward (GVFF) and a double-loop control that is composed of capacitor current feedback (CCF) and a proportional-resonant (PR) controller were proposed. CCF-based resonant damping was analyzed on the basis of a mathematical model. The control including PR and GVFF was also analyzed. The feasibility was verified through simulation. Results show that CCF-based active damping can effectively suppress resonant peak, generating a frequency characteristic similar to that of passive damping, but without power loss. The technique composed of double-loop control and GVFF exhibits various strengths, such as high steadystate accuracy and low total harmonic distortion below 5%, ensuring the high quality of injected grid current. This study can offer a reference for the control of SPGCI.