Inverse Power Factor Droop Control for Decentralized Power Sharing in Series-Connected-Microconverters-Based Islanding Microgrids

Series-connected microconverters have been used to integrate distributed energy resources into grid mains through a single-stage power conversion. When this string converter is switched to islanding operation mode, it is preferred to share the local load demand by series microconverter modules in a decentralized manner. Due to the characteristics of series connection, the well-understood P-f droop and Q-E droop control for parallel distributed generation units in a conventional islanding microgrid is not applicable in this case. To solve this problem, the feasibility of using a simple power factor-frequency inverse droop control for series-connected islanding microconverters is discussed in this paper. The proposed method can achieve simultaneous real and reactive power sharing without the assistance of any communications between series microconverters. Furthermore, the accuracy of power sharing is not affected by the variations of microgrid feeder parameters or the disturbance of the point of common coupling (PCC) nonlinear loads. Simulated and experimental results are provided to verify the correctness of the proposed method.