Robust coordinated control using backstepping of flywheel energy storage system and DFIG for power smoothing in wind power plants

This paper presents a robust coordinated control of a flywheel energy storage system FESS and a doubly-fed induction generator DFIG based wind turbine used to smooth the wind-induced output power fluctuations. The overall system control combines field and voltage oriented control schemes and nonlinear backstepping approach applied first, to the DFIG side converter DSC to regulate the stator active power in order to extract the maximum power from the wind velocity, and reactive power in order to maintain, at the point of common coupling PCC, a unity power factor. Then, to the electrical network side converter NSC to regulate DC bus voltage. Finally, to the flywheel side converter FSC allowing the storage unit to serve as a buffer that stores energy in the case of excess power and retrieves it back into the output in the case of power deficiency. Numerical simulations using Matlab/Simulink software demonstrate the validity of the proposed control strategies in terms of dynamic response, improvement of output power quality and robustness against model parametric variation.