Performance Comparison of Single-Phase Open-Loop Grid Synchronization Techniques

Rapid and accurate estimation of grid voltage parameters is essential for the operation and control of grid-side converters deployed in the grid integration of renewable energy sources. Though phase-locked loops are the preferred technique for this task due to their versatile nature, recently, open-loop grid synchronization techniques also gain much attention due to their unconditional stability, and simple structure. For open-loop techniques, two orthogonal signal components are essential. Obtaining these components in three-phase system is straight forward and simple. However, in single-phase systems, those components are to be generated. In this work, two recently published three-phase open-loop techniques are modified for single-phase applications. Using computationally efficient sliding discrete Fourier transform filter, the required orthogonal components are generated from single-phase grid voltage signal. Additionally, this filter also rejects the harmonics and dc offset present in the grid signal. The modified techniques were implemented in Matlab/Simulink environment and their performance is compared through simulation results. It was found that both techniques perform almost equally well under various grid conditions.