The need to integrate energy storage systems (ESS) with warship power systems to meet future dynamic loads such as high power electric weapons is apparent. This opens up challenges with design integration of ESS with power systems and operational aspects such as steady-state, transient and faulted performance. This paper describes the integration of ESS with a candidate power system as a case study as part of an ongoing timedomain simulation investigation at University College London. The paper describes the models and power management structure of the simulation testbed, that comprises battery based ESS and diesel generators in a hybrid electric power and propulsion system. The results of two scenarios are presented, the first verifies power sharing between a diesel generator and ESS during load levelling under single generator operation, the second illustrates the ability of the ESS to provide ride through power during a generator fault on the main distribution bus. The conclusions suggest that under voltage in the candidate system outside of acceptable limits occurs during fault ride through when in single generator operation.