Fast-response bi-directional power electronic converter for a flywheel energy storage system

In weak grid-connected and autonomous power systems, supplied from wind turbine generators (WTGs), there is a need for short-term storage as the wind speed fluctuates rapidly and consumer loads are unpredictable. The work presented in this paper is part of an EC JOULE funded project in which the University of Leicester, CEGELEC Industrial Controls Ltd. and Rutherford Appleton Laboratory (RAL) are working in close collaboration to develop a 45 kW flywheel energy storage system using an induction machine (IM) vector-controlled drive. The key factors in selecting such a drive, which will operate in conjunction with a WTG of similar rating, is given with a brief description of the drive's features and functionality. It is shown that a fast power response, adequate for smoothing the WTG power, can be achieved. Simulation results, demonstrating the performances of active and reactive power controls, obtained from the vector-controlled flywheel drive, are presented and discussed.