**Rosa Anna Mastromauro**

Department of Information Engineering (DINFO), University of Florence, 50139 Florence, Italy; rosaanna.mastromauro@unifi.it; Tel.: +39-055-275-8650

Received: 29 April 2020; Accepted: 28 June 2020; Published: 1 July 2020

**Abstract:** Synchronization and islanding detection represent some of the main issues for grid-connected photovoltaic systems (PVSs). The synchronization technique allows to achieve PVS high power factor operation and it provides grid voltage monitoring. The islanding detection control function ensures safe operation of the PVS. Focusing on low-power single-stage PVSs, in this study the most adopted and the highest performance synchronization and islanding detection methods are discussed. The role of the synchronization system is fundamental to detect the grid conditions, for the islanding detection purpose, and to manage the reconnection to the grid after a PVS trip. Hence a combined review is advantageous.

**Keywords:**photovoltaic systems; synchronization systems; phase-lockedloops; islandingdetectionmethods
