Two-layer control scheme for a Supercapacitor Energy Storage System coupled to a Doubly Fed Induction Generator

The intermittent nature of the wind represents a challenge to the quality of power of wind generators (WGs). For this reason, many topologies of WGs have been developed to overcome wind fluctuations. Nowadays, the most prevalent topology is the Doubly Fed Induction Generator (DFIG). This technology can compensate for up to +/-30% of the total WG rated power in an attempt to maintain power output constant. In order to extend its operating range, we propose a two-layer control scheme for a supercapacitor energy storage system coupled to a DFIG. The first layer is a decoupled control developed to have the supercapacitor act as a flywheel, thereby reducing output power oscillations. The second layer is an optimization algorithm developed to use the wind forecast data to set the reference power to a small number of levels. The combined scheme is able to effectively command the DFIG to supply optimal, smooth power output. The proposed control scheme is implemented in Matlab-Simulink and simulation results demonstrate its effectiveness. (C) 2011 Elsevier B.V. All rights reserved.