With the continuous development and application of new energy power generation technologies, distribution networks are gradually becoming a hub platform with functions of transmission, distribution, storage, and trading. The operating pressure on distribution networks is increasing. Flexible interconnected devices (FIDs) provide a solution for interconnection of distribution networks, enhancing the power flow regulation capability and fault isolation capability of distribution networks. However, the integration of new energy power generation represented by photovoltaics, along with the retirement of traditional large-inertia synchronous generators, has led to increasingly prominent issues such as reduced overall grid inertia and poor frequency stability. The existing FIDs do not meet the demand for grid inertia support. To address the above issues, this paper proposes a solution based on energy storage-based FIDs combined with grid-forming control represented by virtual synchronous generators (VSG). On the basis of meeting the flexible regulation requirements of distribution networks, this solution realizes inertia support for the AC grid and reveals the intrinsic relationship between virtual synchronous generator control and droop control. Considering that the VSG strategy is prone to overcurrent during fault conditions, a feedforward suppression strategy based on virtual voltage construction is proposed. This strategy can achieve overcurrent suppression in FIDs under fault conditions through power feedforward and voltage feedforward. Finally, the effectiveness of the proposed strategy in power allocation control and low-voltage ride-through is verified through MATLAB/Simulink simulation.