A survey on adaptive protection of microgrids and distribution systems with distributed generators

Microgrids have emerged as a prospective framework that integrates renewable energy sources, energy storage systems, and loads. They can be addressed as a local distribution system with distributed generators (DGs) and have the potential to improve power quality, reliability, and energy efficiency to their consumers in a grid-connected or islanded mode. However, in order to implement microgrids or distribution systems with DGs, some challenges should be faced, especially concerning protection issues. The possible operating modes and the presence of distributed energy resources may make conventional protection schemes ineffective. Therefore, new protection schemes have been developed in the context of microgrids, including the cases of distribution systems with DGs. Thus, this paper presents a comprehensive survey aiming at studies considering this kind of protection. Emphasis has been given to studies associated with adaptive protection, considered by some researchers as a promising solution for microgrid protection. For this purpose, firstly, a microgrid structure is briefly presented. Afterwards, some challenges related to the protection of these systems are also addressed. Moreover, a brief overview of adaptive protection is provided, and then the newly developed schemes found in the technical literature are described. It is worth mentioning that a bibliometric analysis is also presented in this paper, highlighting a substantial growth in publications concerning adaptive protection. Nevertheless, it can be observed that more effort is still needed to obtain a complete solution for the protection of microgrids and distribution systems with DGs. Further attention to matters such as communication failures, cyberattacks, and the presence of energy storage systems should emerge in the next few years.