An Improved Grid-Current-Feedback Active Damping Method for LCL-Type Grid Connected Inverter

In contrast to the L filter, the LCL filter corresponds to a third-order structure which can lead to resonance. Considering the delays caused by digital control in the system, the traditional grid current feedback active damping (GCFAD) has a narrow stable region, which resulting in the poor robustness to changes in grid impedance. In this case, this paper proposed an improved GCFAD which expands the stable region to (0, 0.44fs) by incorporating a delay compensator in the damping loop. This greatly enhances the system's stability and robustness. Furthermore, control parameters are designed based on the system's discrete-domain model. Simulation and experimental results confirm the effectiveness of the proposed control strategy.