A power system of an aircraft includes a hybrid energy storage system with at least two energy storage subsystems each having a different power-energy density, power draw characteristics and/or dissimilar configuration. A primary power unit includes an aircraft engine coupled to an electric motor and a first generator. A secondary power unit is coupled to a second generator. A bidirectional power converter is coupled to the hybrid energy storage system and one or more controllers of the electric motor, the first generator, and the second generator. A power management controller is configured to interface with the hybrid energy storage system and the one or more controllers of the electric motor, the first generator, and the second generator and perform a model predictive control to dynamically adjust one or more electric power flows through the bidirectional power converter based on an engine propulsion power demand of the aircraft engine.