Microgrid Protection Against Internal Faults G HIN G Y IN DB SE EN IC EL LIS UB MP RA G IMA Challenges in Islanded and Interconnected Operation Digital Object Identifier 10.1109/MPE.2021.3057950 Date of current version: 19 April 2021 20 ieee power & energy magazine M 1540-7977/21©2021IEEE MICROGRIDS HAVE GAINED SIGNIFIcant interest over the last 20 years and are perceived as key components of future power systems. Microgrids are defined as distribution networks with distributed energy resources (DERs) (e.g., distributed generators, storage devices, and controllable loads) operating in a controlled and coordinated way. Moreover, microgrids should have clear electrical boundaries and the ability to operate connected to the main power network or islanded. The may/june 2021