Seamless Switching Control under Virtual Synchronous Generator Strategy for Electric Energy Router

Electric energy router(EER) is an essential device in the new distribution network, featuring multiple voltage levels and multiple ports. This paper focuses on the switching control strategy for the grid-connected AC port of EER. As the connected distribution grid is considered a weak grid, the VSG control strategy is employed for the AC port in grid-connected mode. Similarly, in off-grid mode, the AC port also adopts the VSG control strategy to ensure consistency between the two modes. The grid-islanding process under VSG control inherently exhibits a smooth transition, while the grid-connecting process may cause large voltage and current stresses. To ensure a smooth grid connection, this paper proposes a pre-synchronization control strategy based on a predefined coordinate system without a phase-locked loop(PLL), and the feasibility of the control strategy is verified through simulations.