A third creates linear approximations of the nonconvex constraints [42]. Last, the nonlinear constraints are relaxed in order to convexify the problem [43]. All these approaches focus on modeling positive-sequence representations of networks and do not address the additional complexities of modeling unbalanced multi-phase systems that are typical of microgrids. The optimization-based framework presented in this paper was designed to rely on this discussed alternative approach of directly encoding protective feasibility within the microgrid operational problem by constraining fault current to fall within coordination limits. However, in this work, the voltages and currents on the system during faults are explicitly included in the formed optimization problem. Recent work in modeling the short-circuit behavior of grid-connected inverters increasingly focuses on making use of experimental results. Given the current lack of standardization in current-limiting behavior of inverters, this is a necessary step to create accurate models. One such study focuses on validating single- and three-phase dynamic inverter models for load changes against experimental results of commercial grid-forming inverters operating in a stationary reference frame [44]. This study, however, does not take into consideration the current-limiting behavior [45]. Adapting such a model to study short-circuit behavior requires the addition of current-limiting logic, such as described in [23]. Detailed testing of both grid-following and grid-forming inverters under short-circuit conditions has recently been performed in order to provide insight into modeling inverter behavior during faults, including the selection of such logic [46; 47]. These test results were augmented with field data collected during fault events for grid-following inverters deployed on distribution networks [48]. This has resulted in the availability of dynamic inverter models, which were validated against experimental testing [49; 50]. Another development is short-circuit formulations for the fault contributions of grid-connected inverters based on both positive-sequence [51; 52; 53], symmetrical component [54], unbalanced three-phase [55], and hybrid [56] representations. These formulations are an important step towards practical short-circuit modeling of grid-connected inverters, but fall short of a unified framework that can address both grid-following and grid forming inverters in a full, unbalanced formulation. In the case of the presented framework, an optimization-based formulation provides value for inverter-interfaced microgrids by solving for the fault current contribution of inverters running under power factor control mode. The inverter model, which uses a stationary reference frame, is based on [57]. The real and imaginary current contributions become decision variables, whose relative magnitudes are determined by the output bus voltage subjected to current limit constraints. The implementation of the introduced optimization-based framework for short-circuit analysis is provided in PowerModelsProtection.jl ([[https://github.com/lanl-ansi/PowerModelsProtection.jl](https://github.com/lanl-ansi/PowerModelsProtection.jl)]([https://github.com/lanl-ansi/PowerModelsProtection.jl](https://github.com/lanl-ansi/PowerModelsProtection.jl)) accessed on 9 April 2021) (PMsP). PMsP is an extension to PowerModels.jl ([[https://github.com/lanl-ansi/PowerModels.jl](https://github.com/lanl-ansi/PowerModels.jl)]([https://github.com/lanl-ansi/PowerModels.jl](https://github.com/lanl-ansi/PowerModels.jl)) accessed on 9 April 2021) [58] and an addition to the family of free and open-source packages under its umbrella. PowerModels.jl provides a platform to solve and evaluate steady-state power network optimization problems--it decouples problem specifications from the underlying problem formulations, allowing for convex relations to be easily applied.