Speed control for a flywheel energy storage system

Abstract

Accordingly, the invention provides a speed control for a flywheel energy storage system that provides accurate and reliable speed control for long-term operation. The speed control uses a current limiting means that safely limits the acceleration current to the motor for accelerating flywheel, and a rate controller that digitally switches the acceleration current on and off to maintain the desired steady state speed. The rate controller turns the acceleration current off when the flywheel speed is above the desired steady state speed and then turns the acceleration current back on when the flywheel speed falls below the desired steady state speeds. The digital type speed control can be made both more accurate and reliable by using straightforward on/off control about the desired steady state operating speed. The rate controller can operate by measuring the frequency of excitation of a rotational position sensor, and turning the acceleration on or off based on whether the frequency of excitation exceeds a threshold value corresponding to the desired steady state speed. The rate controller could instead operate by measuring the average voltage across one or more electromagnetic coils that are magnetically excited by the rotation of the flywheel and turning the acceleration on or off based on whether the average voltage exceeds a threshold value corresponding to the desired steady state speed.

Dependencies are inferred from the claim text.