A supercapacitor size minimization and energy management strategy for E-STATCOM connected to weak grid

Recently, the rapid integration of renewable energy sources has been reducing power system inertia, which threatens frequency stability. To address this issue, E-STATCOMs with supercapacitor-based energy storage have emerged as a persuasive solution, providing synthetic inertia in weak grids. This paper proposes a novel control methodology to minimize the size of supercapacitors for E-STATCOMs. Firstly, the embedded droop characteristics of virtual synchronous generator (VSG) control are quantitatively analyzed and eliminated, allowing the supercapacitor to store only the necessary energy. Additionally, the proposed supercapacitor energy management strategy tightly couples the stored energy with the VSG control. This enables the automatic management of supercapacitor energy while providing adequate inertial response. A small-signal stability analysis is also performed to ensure the stability of the system when the proposed control strategy is applied. Experimental results verify the effectiveness of the proposed method under various scenarios.