Power Flow Analysis for Hybrid AC/DC Microgrid Islanding Operation Based on an Improved Adaptive Droop Control

Hybrid AC/DC microgrid is consist of AC subsystem, DC subsystem and an interlinking converter (ILC) used for connecting the subsystems. Flexible integration and coordination of different distributed generations (DGs) is essential to meet the increasing demand for electricity. The impacts of frequency and voltage offset caused by load fluctuation have not been considered in the existing control strategies of autonomous microgrid, such as droop control, master-slave control, and average current-sharing control. To address this issue, an improved adaptive peer-to-peer droop control strategy is proposed herein, which is applicable to hybrid AC/DC microgrid in islanding operation mode. Moreover, the corresponding power flow model and solution algorithm are established. The improved control strategy performs well with any load fluctuation, which can not only allocate active power imbalance according to the capacity ratio of all DGs to protect them from overload, but also it is able to maintain frequency and voltage stability in a further step. The effectiveness and feasibility of the proposed method is validated using a bunch of test results on a modified autonomous hybrid AC/DC microgrid.