Stability Analysis and Controller Design of DC Microgrids with Constant Power Loads

DC microgrids consist of multiple power electronic converter units interconnected in a network with sources and loads. They arise naturally in the power systems of electric ships, aircrafts, etc. The main focus of this work is to study the stability of power converters based dc microgrids. These high switching frequency electronics are controlled in a way as to maintain constant voltage, current, or power to the load. Due to their high bandwidth, they can be simplified as a constant power load. For this reason, a nonlinear system arises where it is no longer satisfactory to assume local stability. Methods presented in literature will be reviewed and a method based on Semidefinite Programming (SDP) will be used to simplify the analysis and stability study of these dc microgrids. Furthermore, a robust controller formulation based on a similar SDP is proposed in order to guarantee and expand the stability region using energy storage.