Research on flywheel energy storage system for power quality

This paper presents a design of flywheel energy storage (FES) system in power network, which is composed of four parts: (1) the flywheel that stores energy, (2) the bearing that supports the flywheel, (3) the asynchronous motor/generator, and (4) the AC power converter regulated by a microprocessor controller. The control methods and strategy of the FES system for power quality are introduced in detail. A new rapid method to calculate the amplitude of sinusoidal voltage and current is presented which could improve the performance of the FES system. To realize the high efficiency of the energy conversion and to minimize the torque ripple of the motor/generator, the waveform of the AC power converter output currents is controlled to be sinusoidal by using sinusoidal pulse width modulation (SPWM) control method. During the storage period, the AC power converter accelerates the flywheel storing energy. At the generating times, the AC power converter drives the flywheel to decelerate and then the kinetic energy is transformed into electric energy and returned to power system. This paper also presents an experimental study of the FES system storing energy and synchronous operating with power system, and the control validity is verified through the experimental results.