The portion of distributed generating (DG) units and renewable energy sources (RESs) in power systems with respect to its total power capacity is increasing rapidly; and a high penetration level is expected for the next two decades. In the conventional centralized power generations, in which the synchronous machine dominates, enormous synchronous generators (SGs) comprise rotating inertia due to their rotating parts. The intrinsic kinetic energy (rotor inertia) and damping property (due to mechanical friction and electrical losses in stator, field, and damper windings) of the bulk synchronous generators play a significant role in grid stability.