From active distribution systems to decentralized microgrids: A review on regulations and planning approaches based on operational factors.

• A comprehensive review of recent advancements in the development of ADSs and MGs. • The regulatory requirements for the evolution of passive DNs to ADSs are detailed. • The paper provides some novel factors for transition and formation ADSs to MGs. • The survey assists DSOs to find requirements to participate in day-ahead markets. Restructuring of power systems along with the integration of renewable energy resources in electricity networks have transformed traditional distribution networks (DNs) into new active distribution systems (ADSs). In addition, rapid advancement of technology has enabled the bulk utilization of power generation units and energy storage (ES) systems in distribution networks. The next step in this trend is to decentralize ADSs to microgrids (MGs). This paper aims to present a review on the recent advancements in the development of ADSs and MGs. In this respect, the regulatory requirements and economic concepts, by which the traditional passive DNs are evolved into ADSs, are categorized and illustrated first. Then, the state-of-the-art of ADS formation is detailed based on the novel standpoint of grid operation factors which are involved in deregulated electricity markets at the distribution level. After presenting highlighted projects of MGs across the world, a similar review approach has been adopted to explain the formation of MGs which play a vital role in the decentralization of ADSs. This survey can provide both policy makers and distribution system planners with new perspectives to establish or participate in day-ahead wholesale markets. [ABSTRACT FROM AUTHOR]