A Virtual DC Power Damping Strategy for Grid-Forming Converters

The prevailing volatility and low-inertia characteristics of current new energy power systems lead to a decline in frequency stability. The widely used DC capacitor-based inertial synchronization control lacks a damping link, making it prone to system oscillations under disturbances. To enhance the stability of voltage-source-converter-based high-voltage direct current (VSC-HVDC) transmission systems, this paper proposes a virtual DC power damping strategy applicable to the receiving-end grid-forming converter. The proposed method compensates for the missing damping link by introducing virtual DC power damping, which integrates of DC-side current, rated voltage, and a band-pass filter. By comparing and analyzing the inertia, synchronization, and damping links in the small-signal models of grid-forming converters with and without damping, we confirm that the improved strategy enhances system damping, thereby addressing the lack of physical interpretability in existing methods. Finally, a simulation model of a photovoltaic (PV) system connected to the grid via a multi-terminal VSC-HVDC system is modeled in Simulink. The simulation results demonstrate that the proposed virtual DC power damping strategy effectively suppresses system oscillations under various disturbances.