Coordinated control schemes of super-capacitor and kinetic energy of DFIG for system frequency support

This paper mainly focuses on how to provide frequency supports by the doubly fed induction generator (DFIG) during system disturbances. Two coordinated controls that enable system frequency supports by DFIG-based wind turbines (WTs) are proposed in this paper. The first control scheme seeks to render system support via simultaneously utilizing the energy from the installed super-capacitor between the back-to-back converter of DFIG, and WT rotational kinetic energy (KE). The second one stabilizes system frequency by firstly exerting the installed super-capacitor energy and then WT rotational KE via a unique cascading control. Both proposed coordinated control schemes jointly utilize two virtual inertia sources, namely super-capacitor in the DFIG and rotor rotational mass in the WT to fast provide system frequency support. However, the second proposed one stands itself out by reducing its impaired impacts on the overall wind energy production. Two proposed controls on rapidly providing frequency support are effectively verified and compared in detail by different system disturbances in the DIgSILENT/Powerfactory software.