Low-Frequency Oscillation Suppression Strategy forGrid-Forming Converters Based on Active-Power-LoopVirtual Damping Control

Abstract

 With the rapid growth of renewable energy penetration, grid-forming
converters (GFMs) have become essential for the stable operation of new power
systems. However, the virtual synchronous generator (VSG) features strong
coupling between power and voltage-current control loops due to power
electronic multi-timescale dynamics, which easily induces negative damping
and low-frequency oscillations (LFOs). Under the commonly adopted constant
DC-voltage assumption, the interactions among the active-power and reactive
power loops, together with the influence of the fast voltage-current control
loops, may still result in insufficient damping and LFO. To solve this issue, this
paper proposes a virtual damping control (VDC) strategy for the active power
loop. A reduced-order small-signal model considering the coupling between the
active-power and reactive-power loops is established, while the voltage-current
inner-loop dynamics are neglected under the assumption that they are much
faster than the outer-loop dynamics. A VDC scheme employing band-pass
filtering and phase compensation is designed to generate supplementary power
modulation, providing damping torque to suppress oscillations. Eigenvalue
analysis and time-domain simulations validate the proposed method. Compared
with traditional virtual impedance (VI) control, the proposed VDC effectively
suppresses LFO and improves the damping performance and dynamic stability
of the GFM system