This document provides an overview of grid structure and synchronization for distributed power generation systems. It discusses the increasing demand for renewable energy sources due to environmental problems caused by fossil fuels. The general structure of distributed power generation systems includes different renewable input sources, power conversion units, and output to local loads or utility networks. Synchronization plays an important role in controlling the active and reactive power injected into the grid. The document reviews various synchronization methods, including zero crossing, synchronous reference frame, and phase locked loop techniques. It concludes by emphasizing the importance of grid synchronization algorithms for distributed power generation systems.