The increasing dominance of renewable energy sources in the modern power grids, leads to the installation of power
electronic inverters as they are required to interface these DC and variable frequency sources to the grid. These inverters can provide
additional flexibility to the control of the power grid and are distinguished into grid-forming (GFM) and grid-following (GFL) types.
However, their complex control structures give rise to new threats to system’s stability. This article investigates the transient stability
of these two inverter types. They are studied when connected to an infinite bus and subject to large disturbances, such as three-phase
faults or line disconnections. This investigation begins with an analysis of the various inverter configurations and proceeds to derive
the systems’ swing equations. The analysis is validated using time-domain simulations and stability is studied for a range of operating
conditions and control settings. It is revealed that GFM inverters suffer greater impacts from faults in strong grid conditions which
contrasts to GFL which suffer large impacts from faults in weak grid conditions. Furthermore, it is shown that the inverters’ virtual
inertia and damping coefficients play an important role to their transient stability and ability to ride-through faults.
Keywords — GFM, GFL, synchronization, transient stability