Modeling and analysis of a flywheel energy storage system for voltage sag correction

The US 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 system transients. Power quality problems, such as voltage sags, which arise due to a fault or a pulsed load, can cause interruptions of critical loads. Critical loads include radar systems, pumps and weapon systems. A series voltage injection type flywheel energy storage system is proposed to mitigate voltage sap and maximize the survivability of the ship. The bask 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 flywheel stores energy In the form of kinetic energy and the induction machine is used for energy conversion. The power electronic interface facilitates the bi-directional flow of power for charging and discharging the flywheel through the induction machine. The stored energy is used for sag correction when the critical load sees a voltage sag. Indirect field oriented control with space vector PWM 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 flywheel energy storage system with a power converter interface using PSCAD/EMTDC.