Virtual Inertia Enhancement for Grid Forming Inverters in AC Power Electronics Dominated Grids

In the realm of power electronics, the rise of the Power Electronics-Dominated Grid (PEDG) presents a unique challenge due to its inherent low inertia, a direct consequence of the diminished involvement of rotating masses. This low inertia makes the grid susceptible to various disturbances. Addressing this concern, a model predictive control (MPC) scheme is designed to mimic virtual inertia based on the virtual synchronous generator (VSG) approach. This control scheme ensures that PEDG remains resilient and stable, especially in the face of demand and generation perturbations. Traditionally, the primary control for power electronics-based generators has predominantly hinged on a cascaded PI control scheme to manage both active and reactive power. The proposed scheme employs an MPC for the primary layer while using VSG to emulate the virtual inertia with a refined governor for grid-forming inverters (GFM). A notable advantage of the MPC is its intrinsic bandwidth, which facilitates a superior tracking of the desired rate of change of frequency (ROCOF) under many events, outperforming the conventional PI-based controllers. The modified VSG governor regulates the frequency to its nominal value amidst a spectrum of frequency events. To verify the effectiveness of the proposed scheme, multiple case studies illustrate the prowess of emulating inertia, particularly taking into account the PEDG behavior in the presence of GFM and grid-following (GFL) units considering frequency events.