Modeling and Analysis of a Flywheel Energy Storage System with a Power Converter Interface

A shipboard power system is a stiff, isolated power system. Power is generated locally, and distributed over short distances making the system vulnerable to transients. Power quality problems such as voltage sags, which arise due to a fault or a pulsed load, can cause interruptions of critical loads. This can be of a serious concern for the survivability of a combat ship. A series voltage injection type flywheel energy storage system is used to mitigate voltage sags. The basic circuit consists of an energy storage system, power electronic interface and a series connected transformer. In this case the energy storage system consists of a flywheel coupled to an induction machine. The power electronic interface consists of two voltage sourced converters (VSC) connected through a common DC link. The flywheel stores energy in the form of kinetic energy and the induction machine is used for energy conversion. Bi-directional power flow is maintained by regulating the DC bus voltage. 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 VSC. This paper presents the modeling, simulation and analysis of a flywheel energy storage system and with a power converter interface using EMTDC..