Robust Control of Smart Transformer-fed Grid

The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST-fed grid has high potential to optimize power system and avoid or postpone the reinforcement of distribution networks. However, with the increasing utilization of power converters, the challenges in terms of system stability are encountered. To better understand the problems, this paper firstly develops the models of ST LV converter and grid-forming as well as grid-following converters used in the LV grid. Then, the stability of a ST-fed grid with different types of converters is studied by considering the effect of line impedance. To address the stability issues, a robust control strategy is proposed for the ST LV converter. Simulation results are provided to validate the effectiveness of the proposed control scheme.