Synchronization Algorithms for Grid-connected Photovoltaic Systems under Grid Disturbances

Abstract

The increasing employment of the photovoltaic solar energy demands suitable control techniques in order to ensure a stable and proper connection to the utility grid, especially when disturbances occur, for this reason, the Phase Locked Loop (PLL) technique is used. In this paper, the most commonly synchronization algorithms in grid-connected photovoltaic systems will be presented. The algorithms structures are described and analyzed in detail. The selected algorithms are developed in C-Code and simulated in MATLAB software from MathWorks. The behaviors of the methods are presented and explained under grid voltages disturbances (frequency variation, harmonics presence, voltage unbalances, etc.). The obtained results indicate that each of the tested PLLs has its own advantages and disadvantages, depending on the disturbances occurred into the three-phase utility grid.