Distributed control strategy for global economic operation and bus restorations in a hybrid AC/DC microgrid with interconnected subgrids

With the increasing penetration of distributed generators (DGs) in microgrid (MG), the economic power dispatch (EPD) is a fundamental optimization problem of MG systems. This paper investigates a distributed control strategy, which is consists of local economic control (LEC) and global economic control (GEC), for a hybrid MG with multiple interconnected ac and dc subgrids. The incremental cost (IC) of each DG is selected as a discrete consensus variable and the mismatch of bus parameters, such as dc bus voltage and ac bus frequency, between measured and reference values is assigned as a feedback variable. Thus, both the economic power allocation demand for all DGs and the bus restorations within each subgrid can be simultaneously realized by the proposed LEC. This reduces implementation cost, enhances the operation reliability, and accelerates the converging speed of algorithm. Furthermore, the interconnected subgrids are connected by a set of bidirectional interlinking converters (BILCs) that play a critical role in the power flow performance. Hence, the distributed GEC makes the whole MG system is in global economic operation in accordance with the equal IC principle. The impacts of communication time delays and communication link failures are also analyzed. Finally, the effectiveness of the proposed control strategy is verified by the real-time hardware-in-loop (HIL) tests.