Master-Slave Cooperation for Multi-DC-MGs via Variable Cyber Networks

The reliability of the microgrid (MG) can be improved by interconnecting MGs that are in close proximity, because the power shortfall in one MG can be compensated by the excess power available from other interconnected MGs. For multiple dc MG clusters consisting of a large number of heterogeneous distributed generators (DGs), this article establishes a master-slave cooperation framework containing a two-layer voltage estimator. All master-DGs implement current economical allocation among multiple MG clusters and drive their respective slave-DGs to realize current sharing accuracy. Compared with the previous work, the proposed control strategy has the advantages of simultaneous achievement of accurate current sharing and current economical allocation, short time consumption and faster convergence, and robustness against uncertain communication environments. Moreover, all distributed controllers are allowed to be implemented in a variable cyber network, thus well matching the characteristics of frequent switching operation in MG systems. Sufficient conditions in terms of control time constants for the two-layer cyber network are also deduced to ensure entire system stability. Different cases are tested to verify the effectiveness of the results in MATLAB/SimPowerSystems.