The concept of microgrid (MG) has attracted great attention from the system operators for increasing 3 operational effectiveness as well as providing more reliable, sustainable and economic power system. In this paper, a 4 comprehensive investigation is presented to shine new light on evaluating changes in MG operation from maturity to 5 the future. A great deal of literature studies consisting of the traditional MG architecture, encountered challenges and 6 proposed solutions for overcoming

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... m are all examined in detail. Also, the impact of highly integrated renewable-based 7 energy sources into the power system is analysed by current studies. Moreover, modern MG architecture is extensively 8 investigated from the point of operational flexibility such as energy storage systems (ESSs), combined structure of 9 networked-MGs (NMGs) and demand-side management (DSM). Furthermore, incorporating MG architecture as a grid-10 support service in power system resiliency enhancement strategies is investigated with current literature studies. As a 11 result of this detail investigation, it can be deduced that the power system has witnessed radically new changes and 12 outstanding developments in both generation and consumption side. Renewable power sources have been accepted as 13 the major mile stone in the harnessing electricity and there have a strong trend towards penetrating these types of 14 generation units in MG structure. On the other hand, increased concerns about safety problems and challenges in MG 15 have triggered a huge amount of discussions in the literature. 16