The performance of polytopic models in smart DC microgrids

The huge progress of power electronics technology along last decades opens extraordinary new possibilities for the electric grid. Some examples of what can be achieved with the incorporation of electronic power converters in the system are the penetration of RS (renewable sources) and storage, boosting reliability and power quality, and integrating consumers as part of the system. However, there are still some challenges ahead before the massive deployment of Smart Grids. Lately, a lot of research has been carried out on converters topologies and control strategies in order to get the most out of the microgrids. Therefore, there is a need for methodologies that allow designers to foresee the behavior of these systems comprised of several different power converters governed by the proposed control strategies. In this context, this paper studies the performance of the polytopic models for the analysis of commercial power converters working in dc microgrids. This is a nonlinear modeling technique which integrates small-signal models obtained in different operation points by means of suitable weighting functions. Furthermore, the linear local models can be obtained in a blackbox fashion using suitable two-port models as can be the G-parameters models. This work particularly focuses on the analysis of different power converters using the well-known dc bus signaling control strategy. Thus the modeling of the diverse possible states in which this control technique can operate, and more important the transitions among them, are investigated. In addition, the feasibility of applying system level control techniques to the polytopic models of the converters, such as current sharing or voltage restoration, is considered.