Post Fault Oscillation Damping of Power Synchronisation Control-Based Grid Forming Inverters

Various fault ride-through (FRT) strategies have been implemented in grid-forming inverters (GFMIs), and their ability to support system voltage during faults has been evaluated under various conditions. Each strategy demonstrates different performance characteristics during and after faults. However, less attention has been paid to analysing and improving their post-fault performance. This paper addresses this gap through a comprehensive analysis of the post-fault performance of power synchronisation control (PSC)-based GFMIs, which, as identified in this study, exhibits significant post-fault oscillations under different network strengths, inverter loading levels, and fault impedances. To mitigate this issue, two new post-fault oscillation damping (PFOD) strategies—namely, the dynamic reference power adjustment strategy and the sigmoid function-based adaptive damping strategy—are proposed to enhance post-fault performance without compromising voltage regulation capability. While both methods are effective individually, the best post-fault performance is attained by combining the two PFOD strategies. Furthermore, the performance of the PSC-based GFMI with the proposed PFOD strategies is comprehensively analysed under both balanced and unbalanced network faults, validating the robustness and consistency of the proposed approach. Finally, the improved performance of the proposed strategies is verified in real-time using the IEEE-39 bus network on the OPAL-RT platform for a range of system design and operating scenarios. The findings of this research are expected to serve as a guide for developing specifications and standards for GFMI performance.