This paper details the connection and disconnection of grid-forming inverters with proposed protection measures for smoothing the transients. It proposes a new protection scheme based on imposing a limitation on the difference between the grid and inverter phase angles to avoid rush currents. The protections are validated in an experimental setup of two grid-forming three-phase inverters with a connection to the utility grid. It shows transients of the inverter’s connection process in 1)standalone operation of an inverter, 2)connection of the inverter to an existing micro grid, 3)connection between microgrid and an external grid.
