Control method and system for smooth grid-connected and off-grid switching of grid-forming inverter, and medium

The invention relates to a control method and system for smooth grid-connected and off-grid switching of a grid-forming inverter and a medium, and the method comprises the steps: respectively building a mathematical model of a virtual synchronous generator and a mathematical model of a reference power controller for a frequency modulation module in the grid-forming inverter; establishing a discretization model of the virtual synchronous generator in an actual system and a future prediction output model of the system; selecting a target function based on the established mathematical model, discretization model and prediction output model to establish a phase angle pre-synchronization model; and after the phase angle pre-synchronization is carried out on the network-building type inverter based on the phase angle pre-synchronization model, the network-building type inverter solves the target function in the prediction output model so as to realize grid-connected and off-grid switching of the network-building ty