Research on Adaptive Coordinated Control Method of Low Voltage Flexible DC Interconnection System

In the flexible interconnection system of low-voltage distribution areas, the DC bus voltage can intuitively reflect the active power balance. Therefore, the stability of the DC voltage is a prerequisite for ensuring the coordinated control of each flexible interconnection device (FID) and distributed power source. For the existing centralized control strategies based on DC micro-grids, when the main grid-connected converter fails, they mostly rely on energy storage devices to stabilize the DC voltage, which is not suitable for flexible interconnection system. The decentralized control strategies often adopt voltage droop control for multi-machine parallel connection, but it is difficult to achieve precise power mutual aid in the flexible interconnection system. This paper studies the basic control mode of a single FID and the coordinated control method for the grid-connected system of multiple FIDs, and proposes an adaptive grid-connected/off-grid switching strategy and triggering conditions for FIDs, so as to ensure the system's N-1 operation capability under any working conditions and improve the reliability of low-voltage distribution areas.