Dual Power Hardware-in-the-Loop Simulation of Energy Storage Systems for Shipboard Applications

Energy storage will play an increasingly important role in future surface combatants as specialized loads are introduced on shipboard power systems. These loads may present short-term power consumption and ramps in power that exceed conventional plant capabilities and limits specified in present military standards. This paper discusses experimentation with a Flywheel Energy Storage System (FESS) and the capacitor-based Adaptive Power System (APS) developed at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to explore the synergistic effects of this combination on the dynamics imposed on the AC source, as well as the resulting bus transients seen by the loads, during pulsating load events. The emphasis of this paper is the novel approach of using two Hardware-In-the-Loop (HIL) simulation interfaces for simultaneously testing two different hardware technologies that originally were not designed with a common interface in mind. Interface stability, including effects of the HIL interfaces, is also evaluated to ensure system stability will be maintained when the full system is integrated. Selected results will illustrate the positive impacts of using multiple energy storage systems to temper the impact of extreme dynamic loads on the power plant. This includes examination of the bus impedance of the full system to gain insight on the system performance as a function of each subsystem's characteristics. Moreover, the results demonstrate the benefit of the APS to significantly reduce the required DC link capacitance of the FESS, thereby reducing overall size and weight of the total energy storage required in the system.