Trends in dc Microgrids: From the control and protection perspective

Microgrids (MGs) are driving us toward more resilient power grids. They can operate independently from the upstream power grids and provide a reliable source of power to their customers. Conventionally, ac MGs have been deployed to increase the reliability and resilience of power grids or provide power to remote areas where connection to an electric power grid is not possible. However, more recently, dc MGs have gained much attention due to a number of advantages. These advantages include a higher efficiency and power transfer ratio compared to their ac counterparts as well as simpler control and operation since, in dc systems, only voltage and power are the control objectives; the reactive power and frequency of ac systems are not of concern anymore. However, the dc MG still faces some control challenges, especially from the perspective of voltage regulation and power sharing. Moreover, the protection of dc MGs is more challenging than that of ac ones.