Research on Discharge Control Strategies for FESS Array Based on DC Parallel Connection

Flywheel Energy Storage System (FESS) , which stores energy in a rotating mass, is now considered a promising technology for many applications due to its significant advantages versus chemical batteries. Integrating multiple modular FESS units to form a FESS array is a suitable solution to attain large capacity energy storage. This paper presents a FESS array topology for an uninterruptible power supply (UPS) system. And three discharge control strategies were adopted, i.e., equal power strategy, equal torque strategy and equal time duration strategy. The above strategies were verified by simulation in Matlab/Simulink, and the results indicate that all of the three can control the discharging process of the FESS array accurately, stabilize the dc bus voltage and make voltage-sensitive load not affected by grid power interruption. However, the equal time duration strategy can make the FESS array work longer while the equal torque strategy is more simple and practical in operation.