Thanks to the push towards sustainable energy, modern electric networks are witnessing the spread of photovoltaic and wind renewable sources, which are the main responsible for the great and great diffusion of converter-interfaced distributed generators. The number of these converter-interfaced sources is increasing at such a level that it is having a significant impact on the stability and operation of the electric grids. This raises the issue of properly integrating power converters for energy-source interface into the electric grid, so that they can concur to its stable and performing control. The very rich scientific production testifies that such a question is greatly attracting the attention of the international scientific community. Grid-connected converters interfacing distributed generators are classified according to their operation and performed task, but the scientific literature has not still provided a unique classification. This paper makes an overview of the two main classifications used in the literature, highlighting the peculiarities of the two classifications, their similarities and differences, and describing the different categories of converters, their tasks, up to date control strategies and solutions for the most important issues found in the recent literature. Moreover, in the attempt of providing a merge between the two classifications and avoid confusion about the concept of “grid forming”, used with different meaning by both the classifications, a new nomenclature for converter categories is proposed. Given that most of research lines try to conform the new concepts to the traditional ones, focus is posed on the distributed generators with traditional non-communication based primary control.
