A grid synchronization method for droop controlled distributed energy resources converters

With the high penetration of distributed generation system, many control methods have been widely discussed for managing the power flows between these distributed energy resources converters in islanded or grid-connected operation modes. The grid synchronization method has been also elaborately discussed for single grid-connected converter. However, it is not often explored for the multi-converter oriented system. In this paper, a grid synchronization method for the multi-converter oriented distributed generation system is proposed. The proposed grid synchronization method can cooperate with P - f, Q - V droop controls, and all the distributed energy sources converters regulate their own phase angles and voltage magnitude at the same speed. Thus the original power flow determined by these droop controllers can be maintained during the operation of grid synchronization. Its operation principle is explained, and experimental test results are presented to validate the effectiveness of the proposed grid synchronization method.