Inverse Distribution of Inertia and Damping for Mitigating Low-Frequency Oscillations in Power Systems

The large-scale integration of low-inertia converter-interfaced generations (CIGs) has reduced the power system's frequency robustness and increased the risk of frequency instability. Thus, it is imperative to allocate additional (virtual) inertia and damping in power systems to maintain and enhance frequency response. However, current research in this area typically relies on complicated numerical algorithms, making the optimized results difficult to interpret and only applicable to specific cases. In light of the above, this paper establishes a more general and comprehensible principle concerning the allocation of inertia and damping. Firstly, it is demonstrated that when the total amount of additional inertia and damping is constant, their distribution within the system predominantly influences the disparity in the bus frequency, which manifests as low-frequency oscillations (LFOs) between generation devices. Then, it is revealed that for a weakly damped oscillation mode involving two groups of relatively oscillating devices, if the oscillation amplitudes within each group are approximately equal, distributing inertia and damping inversely (more damping to the group with less inertia, and vice versa) assists in mitigating the corresponding oscillation. This distribution is different with the conventional setting that inertia and damping are uniformly distributed. Case studies are provided to validate these conclusions.