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Wednesday, 19 July 2017

Modeling and Control of Flywheel Energy Storage system for Uninterruptible Power Supply


1.      Control systems
2.      DC-AC power conversion
3.      Energy storage
4.      Flywheels
5.      Load flow control
6.      Pulse width modulated power converters
7.      Permanent magnet motors


Fig. 1. Basic circuit diagram of the FESS in UPS.

Fig. 2. Flywheel speed in charging mode.

Fig. 3. Electromagnetic torque of IPMSM.

Fig. 4. Power grid voltage sag and outage

Fig. 5. Power failure detection signal.

Fig. 6. Flywheel speed in discharging mode.

Fig. 7. DC bus voltage

Fig. 8. 3-phase voltage of critical load (phase to ground) without FESS.

Fig. 9. 3-phase voltage of critical load (phase to ground) with FESS

This paper presents a modeling and control method of FESS in UPS system. A cost effective and reliable flywheel design is brought forward to prove the possible mass utilization of FESS in industrial applications. The control algorithm of FESS is described with detailed block diagram, including the torque control of IPMSM that driving the flywheel, voltage sags and outage detection and DC bus regulation. Simulation results are presented to validate the control strategy. Future tasks will include control strategy on mitigating unbalanced voltage sags, parameter variation of IPMSM and experiment verification of the control methods.

[1]   R. BROWN Daryl and D. CHVALA William, "Flywheel Energy Storage An alternative to batteries for uninterruptible power supply systems," Pacific Northwest National Laboratory, ETATS-UNIS, Richland, Washington, US, 2004.
[2]   Ralph H Jansen. Timothy P Dever, "G2 Flywheel Module Design," University of Toledo 2801 W. Bancroft St. Toledo, Ohio, US, Tech Rep. NASA/CR-2006-213862, 2006.
[3]   Active Power Corp. (2008), "Quantitative Reliability Assessment of Ball Bearings versus Active Magnetic Bearings for Flywheel Energy Storage Systems," [Online] Available:
[4]   S. Morimoto, M. Sanada, and Y. Takeda, "Wide-speed operation of interior permanent magnet synchronous motors with high-performance current regulator," Industry Applications, IEEE Transactions on, vol. 30, pp. 920-926, 1994.

[5]   Barbara H Kenny and Peter E Kascak, "DC Bus Regulation with a Flywheel Energy Storage System," NASA, John H. Glenn Research Center, Lewis Field Cleveland, Ohio, US, Tech Rep. NASA TM-2002-211897-REV102PSC–61, 2003.