Hierarchical control of active hybrid energy storage system (HESS) in DC microgrids

Energy storages can be characterized based on energy and power densities, ramp rate, etc. Hybridization takes advantages of all energy storages to enhance system performance. Hierarchical control which is comprised of both centralized and distributed control is proposed for HESS operation in this paper. In normal state, system operates with energy management system. The central controller is used to coordinate the power sharing among various energy storages based on their characteristics and operating statuses. In case of communication failure, distributed control which operates with local information is to be activated. The bus voltage is used as indicator for system power balance to realize distributed control of system units. MATLAB/Simulink is used for the verification of the proposed methods.