# Understanding Microgrid Sustainability: A Systemic and Comprehensive Review
## 2 Overview of Existing Microgrid Literature  
There is still no consensus on the concept of microgrids in the literature. All existing definitions can be broadly regrouped in two categories: \"energy microgrid\" and \"community microgrid\". These two categories and their relations to the fields proposed in this work are shown in Figure 2.  
Energy microgrids, shown in red in Figure 2, gather the energy and information field. An example of a definition falling into this category is the one given by the European Microgrids project [21]. It states that microgrids are \"_Low Voltage distribution networks comprising various distributed generators, storage devices and controllable loads that can operate either interconnected or isolated from the main distribution grid as a controlled entity_\". Community microgrids, shown in blue in Figure 2, gather the social and financial fields. An example of a definition is given by [PERSON] [22]. It states that \"_A community microgrid is connected with its community through physical placement and can be partially or fully owned by said community. [...] Considering the social dimension, a 'community microgrid' can be viewed as a microgrid with the key objectives of achieving economic, social and environmental benefits in community electricity supply and distribution_\". This review seeks to reconcile these two definitions of microgrids as a basis for analysis of their sustainability. Figure 2 depicts this approach as the gray and purple areas at the intersection of these definitions. The gray areas show microgrid models and visions that partially integrate these definitions. The purple zone represents the objective of this review. While there are many highly detailed recent reviews on microgrids' operations and different architectures, there is still a gap in the global view. These tend to focus on either energy microgrid [23; 24; 25; 26] or community microgrid [27; 28; 29], but rarely both, or only in brief. The reconciliation of the energy and community microgrids views is not straightforward. Many articles in the literature addressing microgrid sustainability through systemic analysis tend to rely on qualitative approaches based on study cases or common sense inference [30]. These systemic analyses tend not to get into the technical details of the  
Figure 2: The two definitions of microgrids and their fields. microgrid and its operation, given its multidisciplinary nature. In contrast, analytic articles addressing microgrids then deduce laws from mathematical models, which naturally require assumptions for simplification [31]. As with all multidisciplinary scientific work, inference and deduction combined with systemic and analytic approaches lead to conflicting views of the same problem. As our approach tries to reconcile a systemic inference while keeping the precision of the analytical deduction, we will tie the concept of microgrid sustainability to the issues it faces. The issues of microgrids will be described based on its four fields, as shown in Table 1.  
In this work, the definition of a sustainable microgrid is capable of addressing all the issues of its fields in a satisfactory manner at the time of analysis. The purpose of what is sufficient for each field depends on each case, leaving the possibility of qualitative analysis. However, it must be translated in thresholds, compatible with analytic tools such as classification. Other reviews of microgrids take into account a maximum of parameters for a transdisciplinary study of microgrids.