An Open-Loop Grid Synchronization Approach for Single-Phase Applications

From the control point of view, synchronization techniques are divided into two major categories: Open-loop and closed-loop methods. Roughly speaking, open-loop synchronization (OLS) approaches are not as popular as closed-loop ones, probably because they suffer from a poor performance in the presence of frequency drifts. This is particularly true in single-phase applications, where the lack of multiple independent input signals makes the implementation of the synchronization technique difficult. The aim of this paper is to develop an effective OLS technique for single-phase power and energy applications. The proposed OLS method benefits from a straightforward implementation, a fast dynamic response (a response time less than two cycles of the nominal frequency), and a complete immunity against the DC component in the grid voltage. In addition, the designed OLS method totally blocks (significantly attenuates) all harmonics up to the aliasing point under a nominal (off-nominal) frequency. The effectiveness of the designed OLS technique is verified using comparative experimental results.