Research on operation strategy of wind-solar-storage direct current microgrid based on droop control

Droop control is an important control strategy for microgrids, which has the advantages of power regulation capability without relying on communication systems and "plug-and-play" functionality. However, the DC microgrid with traditional droop control has small inertia, and the system frequency may experience sudden changes when the system power fluctuates. This may affect the security and reliability of the system operation. This paper incorporates a virtual synchronous generator control method into the droop control to suppress the voltage and frequency transients caused by load switching during island and grid connection modes. In order to prevent direct connection of inverters from causing shock currents and equipment damage due to deviations in microgrid and grid-side voltages. This paper adopts a grid-connected pre-synchronization control founded on the Phase-Locked Loop. This strategy ensures that the voltage phase and frequency of the inverter side remain synchronized with the grid side. Achieving smooth switching between microgrid islanding and grid-connected modes.