A Grid Synchronization Method for Droop-Controlled Distributed Energy Resource Converters

The microgrid is a very effective way of integrating various distributed generation resources into the ac power system. To provide electric power of high reliability, the converters in the microgrid often rely on autonomous droop control methods to reduce their dependence on communication and need to operate in both the islanded mode and the grid-connected mode. In this paper, a grid synchronization method for a multiconverter distributed generation system is proposed. The proposed grid synchronization method allows multiple droop-controlled converters to adjust the frequency, phase, and amplitude of their output voltages to prepare for grid connection. The entire synchronization process can be executed with very limited communication requirement. This paper provides detailed explanation on the proposed grid synchronization method. Experimental test results are presented to validate the effectiveness of the proposed method.