Enhancing Frequency Stability of Weak Grids with Modified Distributed Virtual Inertia Method

In small-scale power systems, distributed virtual inertia (DVI)-based converters can effectively participate in primary frequency regulation. In this method, the synthetic inertia provision is fulfilled by discharging the preserved energy of dc-side capacitors employed in grid-interactive converters. Nevertheless, the eigenvalue analyses provided by small-signal state-space model of the converter reveal that the DVI function induces instability to the converter operating in weak grid connection. To address this issue aimed at improving grid frequency stability during frequency events, a new compensator is presented in this work. The compensator is designed so as eliminates the negative effect of DVI regulator on system stability. The effectiveness of proposed approach is illustrated by the time-domain simulations in MATLAB. The results show that the frequency rate of change following a frequency perturbation is enhanced by 40.38% compared with the scenario in which the synthetic inertia functionality is nullified.