In recent decades we have been witnessing an ever-increasing penetration of generation from renewable sources interfaced to the grid via converters. As generation from rotating machines is replaced, the inertia of the system is reduced, and with it, the ability of the system to restore the nominal operating condition following disturbances and contingencies is reduced. Distributed generation converters will increasingly have to be able to support the grid, generate voltage references, feed short-circuit currents and possibly also provide black start services.

For this reason, ever-increasing attention is being paid to the development of innovative control techniques for converters. While in physical terms, converters lead to a reduction in inertia and tend to destabilise the grid, they also offset this effect by their being fully controllable. Through the development of appropriate controls, converters can therefore have very varied behaviours and bring benefits and support to the grid. This report describes the main mathematical tools underlying stability analysis and some of the converter control techniques that are most studied in the literature, with a particular focus on their dynamic properties. Among the most interesting properties analysed are the dynamic response to large equilibrium perturbations, the black start capability and the ability to operate in plug and play mode.