Frequency superimposed energy bifurcation technology for a hybrid microgrid

A conventional microgrid comprising both ac and dc components undergoes a significant power loss during the multistage conversion process. To overcome the problem of reduced efficiency in a conventional microgrid, a significant attention has been drawn towards the structure of the hybrid ac/dc microgrid. The precise power management in a hybrid microgrid is relatively complicated due to the presence of the dc sub-grids in the architecture. In dc sub-grids, the converter power can only be controlled by regulating the output voltage. However, the computation of the reference voltage turns out to be a challenging task due to the system resistance. The complexity further increases as the line resistances associated with the interlinking converter differs. Addressing this issue, to implement an efficient power management strategy in a dc sub-grid, a superimposed virtual frequency based control variable is proposed in this work. The proposed control variable remains unaffected by the system impedance which helps to attain an efficient power bifurcation. The study extensively evaluates the maximum exchanged power, storage utilisation factor, and circulating power among the multiple interlinking converters. The proposed strategy efficiently manages the bidirectional power flow between the ac and dc sub-grids.