Advanced Grid Voltage Synchronization Method Under Abnormal Grid Conditions

In this paper, a novel estimation of the grid voltage using the dual enhanced SOGI-enhanced FLL (eSOGI-eFLL) structure is proposed. In eSOGI, a variable feedback gain is added to provide the required degree of freedom, thus the fast response of eSOGI is achieved. Moreover, to improve the estimation performance, the eFLL output is modified with an additional compensation component which is found from eFLL input and new gain. The effectiveness of the proposed method is verified by the simulation results under various grid fault events, such as voltage sag, phase angle jump, and step change in grid frequency.