In the recent decade

a significant increase in the penetration level of renewable energy sources (RESs) into the distribution grid is evident due to the world's shift towards clean energy and to increase the reliability or inboard manner resiliency of electrical distribution system. RES based microgrids are the most favorable option available

especially to enhance resiliency. However

the integration of RES over the distribution grid would hamper the grid stability due to its stochastic nature under normal conditions. During extreme weather conditions

RES behavior is completely uncertain. Hence there is a need to eliminate the adverse effects caused by the RES and make the distribution grid more reliable and stable under normal and resilient conditions. To address these issues

many researchers proposed several methods to place energy storage units (ESUs) and microgrids (RES integrated)

which can support critical loads at an optimal location in the distribution system during normal and extreme conditions

respectively. The aim of this article is to consolidate and review the research towards various approaches to formulate the problem (optimal location

allocation

and operation of ESU and microgrids to face regular and extreme weather condition) and tools to solve it for enhanced system flexibility and resiliency. Based on the review

a generalized methodology has been designed to adapt the inputs and address both conditions. At the end of the review

future aspects for ESU to strengthen resistance and resiliency of its own are presented

which can be helpful to further improve the reliability and resiliency of the distribution system.