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This study proposes a versatile decentralised control strategy for the direct current (DC) microgrid based on the DC bus signalling method. Performance of the proposed control strategy is investigated under various generation and load disturbances in both grid-connected and islanded operation modes of the DC microgrid. The studies are conducted using a realistic DC microgrid study system simulated in the PSCAD/EMTDC software. The study results indicate that the proposed control strategy: (i) effectively maintains the power balance in the DC microgrid, (ii) effectively limits the DC bus voltage deviations under large disturbances, (iii) improves stability and dynamic response, (iv) does not curtail renewable power generation unless it is necessary, (v) does not require excessively large grid-tied converter and battery energy storage systems, and (vi) enhances system reliability, flexibility, modularity, and expandability.

A direct current (DC) microgrid has become a superior power system in recent years due to the development of DC loads and higher efficiency of DC systems. One of the challenging problems on DC microgrids operation is protection, and it is still a particular concern associated with the challenges of developing a proper protection scheme owing to its characteristics and lack of standards in DC protection. Due to the significant increasing interest on DC microgrid; this study investigates protection problems and schemes that need to be addressed in modern power systems involving DC microgrids. This study analyses and presents a comprehensive review of the most recent growth in the DC microgrids protection. Additionally, the fault characteristics of DC microgrids, the impact of constant power loads, the protection devices and several proposed methods to overcome the protection problems are discussed. The differences between the proposed protection methods for the DC microgrids are also discussed.