A Generalized Design Criterion of Filter-Based Stabilizing Control of ST-Fed LV Grid

Despite the Smart Transformer's (ST) significant advantages in addressing system-level challenges, control-level issues, especially stability issues arising from the increasing penetration of inverter-based renewables, remain crucial. Existing methods, like filter-based active damping and virtual impedance, have been explored in literature to improve the stability of low voltage (LV) ST-fed grids. However, most of these approaches are tailored to specific stability concerns, lacking the generality needed for comprehensive designs. To bridge this gap, this paper proposes a generalized filter-based stabilizing control for the ST LV converter, using the biquadratic filter. A general design criterion is proposed, grounded in pole-zero compensation within a multi-input multi-output (MIMO) system framework. This design criterion aims to determine an optimal stability region for parameter design, with the potential to be applied to a broader range of second-order filters with poles and zeros. Both theoretical analysis and testing validate the effectiveness of the proposed control strategy and design criterion.