Nowadays because of reducing fossil energy resources, environmental issues, tendency to use more renewable energy sources and reduction of casualties, tendency to transform power system into smart power system has increased and a lot of research has been done in this field. Ability to properly exploit renewable resources and distributed generations and their aggregation with the traditional power systems in the form of microgrid is an important step in making smart grids. Microgrid is a small-scale power grid which has distributed generation resources, local energies, and a controlling system and it can be connected to traditional power network or it can operate independently. Defected ground structures are connected to the electricity network or microgrid by electronic converters. Most of the time Voltage Source Inverters are used as electronic power interfaces. Accordingly, in recent years the control of parallel inverters in the form of microgrid has been studied seriously. Proper adjustment of controller parameters in order to achieve system sustainability and proper performance against load charges is very important. The most important problem in optimizing the parameters is the complexity and non-linearity of the control system. The small signal model is a common way to design these parameters. In this session we generally examine the sustainability of small signal, transition of a sample microgrid including two distributed sources based on parallel inverter and their response analysis to load changes and operation of microgrids and we examine effect of various control parameters which are used in the microgrid structure on power sustainability, voltage, frequency and current. Therefore, in this research, sustainability of microgrids is first examined and analyzed. Then by introducing and modeling the studied microgrid and analyzing the small signal sustainability, the effective parameters of the model and by using particle swarm optimization in order to improve sustainability and increase optimal power quality will be determined and finally a robust-fuzzy control in order to increase control efficiency against uncertainty in network parameters and load is proposed. The effectiveness and efficiency of the method by optimizing the parameters obtained through simulations during the time will be proved. In these simulations, the effect of load change and change of microgrid operation and how the controller responds these changes and at the end, the sustainability analysis of the controller with the optimal parameters obtained through the align="left" Keywords: microgrids, voltage source inverter, stability analysis, small signal model, optimization