## 1 Introduction  
In the coming years, it is expected that classical electrical grids will drive forward to a smarter, more flexible, reliable, efficient and bidirectional format leading to a more complex framework. All of these benefits should be supported by an appropriate infrastructure. In this context, microgrids [1; 2], and mainly alternating current (AC) microgrids, play a key role in a new electrical paradigm pushed by the increasing penetration of Distributed Energy Resources (DER). This paradigm will deal with the variability and unpredictability associated with DERs and local demand fluctuations. This versatility generates a way to delay the renovation of an aged infrastructure that cannot withstand an existing rising demand [3]. A new outline, constituted by several interconnected AC/DC (direct current) microgrids or nano-grids [4], conventional energy sources, and loads will create future viable smartgrids [5]. Microgrids can provide potential economic and environmental benefits, but their implementation implies great technical difficulties in control, energy/power management and protection. Some authors focus on the low level loops for the inverters' operation; AC droop [6; 7; 8; 9], voltage and current control loops [10; 11; 12]. Other ones concentrate on the high management level based on cooperative distributed strategies [13; 14] or optimal-smart operation [15; 16; 17; 18]. Considering the previously mentioned antecedents in the literature, the authors of this paper consider it very relevant to pay attention to fault protection [19; 20] and secure operation in seamless transference between operation modes [21; 22; 23; 12]. On one hand, in traditional AC four-wire distribution systems, protective device coordination during faults is achieved by selecting appropriate circuit-breaker current-time characteristics under clear regulations. This choice does not imply intercomponent communication [21; 24] and assumes high short-circuit power levels [24]. However, the situation is the opposite in the case of microgrids based on power electronics, the over-load capability being, hereinafter Fault Current Limitation (FCL), constrained. In a microgrid context, it should be adaptive and fast in terms of voltage and current limitations [25], and should be able to behave sinusoidally to not affect the response of conventional protective breakers. On the other hand, inverters in a microgrid can play two main roles: one as a controlled voltage source and the other as a controlled current source [26], and can adopt two control hierarchies, master-slave or peer-to-peer [27]. In addition, in the peer-to-peer hierarchy, the conventional AC droop voltage control strategy, based on the steady-state or quasi-static power transference model between AC sources [6; 28], is a widely applied alternative to face both operation modes (grid-(dis)connected) and parallelize various inverters, but generates poor dynamics, mainly in grid-disconnected operation. This last situation get worse with the typical use of low-pass filters to emulate synchronous generator mechanical inertias [28]. The combination of droop-based control with the use of virtual impedances is a widespread mechanism to support the soft-start challenge under a peer-to-peer hierarchy [29; 30]. Furthermore, conventional AC droop control presents low adaptability when the operation point differs significantly from the planned rated point. In this situation, the recent use of dynamic phasors can be used to improve the adaptability of conventional AC droop control strategies [31]. The motivation of this paper regards considering strategies that provide FCL capabilities in both operation modes. It can be found in [24; 32; 33] examples based on separating the fault from the grid rapidly but without an AC fault management strategy. However, previous examples as well as others, focus on faults at the DC-link of the inverter [34], observing the effect on the AC side. On the other side, others references concentrate directly on DC microgrids [35; 36; 37].