Phase-Tracking Robust-Synchronization-Loop for Grid-Connected Converters

This paper presents a novel phase-tracking robust-synchronization-loop (RSL) to track the phase and frequency of the grid voltage. A detailed analytical model of the proposed RSL algorithm is presented. Further, a state-space small-signal model is developed, including the dynamics of a grid-connected converter and its controller. From the small-signal analysis, it is shown that the eigenvalues associated with the states of the RSL remain in the left half-plane even for a very weak grid condition with a grid impedance of 1.0 pu, thus, it provides better stability property with the grid-connected converters. In order to show the effectiveness of the proposed RSL, simulation results are provided for different scenarios of the grid conditions such as voltage and frequency disturbance, unbalance grid condition and grid faults. Further, the performance of the RSL algorithm is tested by experiment in lab. The results show that the proposed method effectively tracks the phase and frequency of the grid voltage and maintains the good synchronism of the converters during different disturbances.