The U.S. Navy is looking for methods to maximize the survivability of combat ships during battle conditions. A shipboard power distribution system is a stiff isolated power system that is vulnerable to voltage sags, which arise due to faults or pulsed loads, which can cause interruptions of critical loads. A series voltage injection type flywheel energy storage system (FESS) is used to mitigate voltage sags and maximize the survivability of the ship. The basic circuit consists of an energy storage system, power electronic interface, and a series injection transformer. In this case, the energy storage system consists of a flywheel coupled to an induction machine. The stored energy is used for sag correction for the critical load. Indirect field-oriented control (IDFOC) with space-vector pulsewidth modulation (SVPWM) is used to control the induction machine. Sinusoidal PWM is used for controlling the power system side converter. This paper presents the modeling, simulation, and analysis of a FESS with a power converter interface using PSCAD/EMTDC.