Analysis of Flywheel Energy Storage Systems for Frequency Support

Abstract

Flywheels have been used to store energy in rotation for centuries. However, they were previously not suited for storing electrical energy because of their lower operating speed. However, with AC to DC converters, the flywheel energy storage system (FESS) is no longer tied to operate at the grid frequency. FESSs have high energy density, durability, and can be cycled frequently without impacting performance. Therefore, the FESS is suitable for delivering high power and low energy content to the grid. These traits make it ideal for supporting short term frequency regulation in power systems. This thesis proposes a stepwise power reference control scheme that delivers rated power and 1-2 MW below rated power to arrest frequency droop. This stepwise power reference is paired with traditional frequency dependent control to arrest the frequency early and provide fast stabilization.