Synchronization in single-phase grid-connected photovoltaic systems under grid faults

The highly increasing penetration of single-phase photovoltaic (PV) systems pushes the grid requirements related to the integration of PV power systems to be updated. These upcoming regulations are expected to direct the grid-connected renewable generators to support the grid operation and stability both under grid faulty conditions and under normal operations. Grid synchronization techniques play an important role in the control of single-phase systems in order to fulfill these demands. Thus, it is necessary to evaluate the behaviors of grid synchronization methods in single phase systems under grid faults. The focus of this paper is put on the benchmarking of synchronization techniques, mainly about phase locked loop (PLL) based methods, in single-phase PV power systems operating under grid faults. Some faulty mode cases are studied at the end of this paper in order to compare these methods. It is concluded that the Enhanced PLL (EPLL) and the Second Order Generalized Integrator based PLL (SOGI-OSG PLL) technique are the most promising candidates for future single-phase PV systems due to their fast adaptive-filtering characteristics.