Grid synchronization techniques for converter interfaced distributed generation systems

This paper briefly reviews the synchronization techniques for single-phase and three-phase converter-interfaced distributed generation (DG) systems. These techniques are compared in terms of their capability in tracking the grid frequency variations in the presence of low order harmonics and unbalance conditions. The techniques introduced in this paper are applicable for a wide range of converter-interfaced DG units, e.g. wind, photovoltaic, and fuel cells, and also in active power filters and uninterrupted power supplies.