Analysis of Active Damping Methods for Power-Synchronization Dynamics Considering Impacts of Different Inner Loops

This article evaluates active damping methods for power-synchronization dynamics in grid-forming (GFM) converters, including frequency-to-active-power (FtP), active-power-to-frequency (PtF), and q-axis-voltage-to-frequency (VqtF) controls. Beyond stability-oriented damping analysis, their impacts on inertial response and damping effectiveness under different inner-loop control structures are systematically evaluated. It is revealed that when inner loops employ virtual-admittance-current control and open-loop voltage control, the PtF and VqtF methods share the same damping mechanism and exhibit equivalent characteristics. In contrast, under vector-voltage-control-based inner loops, a tradeoff emerges: the PtF method provides effective damping but prolongs the inertial-response settling time, whereas the VqtF method has a negligible impact on inertial response but offers limited damping in the low-frequency range. To address this tradeoff, a hybrid damping scheme combining PtF and VqtF is proposed, achieving effective damping while preserving inertial response capability. Simulation and experimental results validate the effectiveness of the proposed approach.