A hybrid adaptive fuzzy control strategy for DFIG-based wind turbines with super-capacitor energy storage to realize short-term grid frequency support

In general, the power systems with high penetration of renewable energies result in a system with a relatively low moment of inertia, and can be susceptible to significant frequency variations. However, the virtual inertia of wind power which imitates the kinetic inertia of synchronous generator can be used to improve the system dynamic behavior. This paper presents a novel hybrid adaptive fuzzy control scheme that utilizes both the rotating mass of the DFIG and a super-capacitor bank as the virtual inertia sources for DFIG-Based wind energy applications to provide short-term frequency regulation support. First, in order to compensate the intermittent nature of the wind, a super-capacitor is connected to the DC link of the back-to-back converters and an additional adaptive fuzzy controller is added to the supper-capacitor system controller to realize the short-term frequency support. In a ddition, to reduce the cost of the supper-capacitor, by utilizing the rotating mass of the DFIG, an adaptive fuzzy controller is also designed according to the deviation and derivative of the grid frequency for the active power regulation of the rotor-side converter to provide the optimal virtual inertia. Furthermore, a coordination optimizer is designed to obtain an optimal trade-off between the energy output from the DFIG rotating mass and the energy from the super-capacitor. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed control strategy.