Microgrids as the "building blocks of smart grids"are predicted to play a major role in the future, as they are capable of improving the technical, environmental and economic fields in large power systems. This paper proposes a new formulation for the islanded Microgrid reconfiguration in order to improve voltage stability index. The formulated problem is solved using harmony search algorithm. The increasing loadability index of microgrids in the islanding mode is more important than the index

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... f the grid-connected mode due to its operational limitations such as reactive power generation. In addition, this paper presented an improved indicator to estimate the voltage stability margin of islanded microgrid system based on the system's operational constraints both saddle node and limited induced bifurcations, called as cat_VSIIMG. The cat_VSIIMG which is validated by verified CPF method for IMGs is called the maximum load ability margin of IMG,  IMG. Performance and effectiveness of the proposed method are demonstrated on 33-bus test system. The results show that the implementation of appropriate IMG reconfiguration problem formulations will facilitate a successful integration of the microgrid concept in power systems. Keywords: islanded microgrid; islanded microgrid reconfiguration; reduced islanded microgrid network; voltage stability; ZIP model. Nomenclature A. Parameters and Variables ij r the i-j line resistance ij x the i-j line reactance ij L the i-j line inductance