Autonomous Operation of a Hybrid AC/DC Microgrid with Multiple Interlinking Converters

Applying conventional dc-voltage based droop approaches for hybrid ac/dc microgrids interconnected by a single interlinking converter (IC) can properly manage the power flow among ac and dc subgrids. However, due to the effect of line resistances, these approaches may create a circulating power as well as overstressing the ICs in the case of employing multiple ICs for interconnecting the ac and dc subgrids. This paper proposes an autonomous power sharing approach for hybrid microgrids interconnected through multiple ICs by introducing a superimposed frequency in the dc subgrid. Hence, a suitable droop approach is presented to manage the power among the dc and ac sources as well as ICs. The outcomes are proportional power sharing, preventing circulating power and overstressing the ICs as well as acceptable dc voltage regulation. Furthermore, the maximum transferred power by the ICs can be improved by employing the proposed approach. The effectiveness of the proposed approach is evaluated by simulation.