Three-phase grid synchronization techniques for grid connected converters in distributed generation systems

This paper briefly reviews the synchronization techniques for 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. Moreover, this paper introduces a new three-phase adaptive notch filtering (ANF) synchronization technique. 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.