A novel ectropy-based control scheme for a dfig driven by a wind turbine with an integrated energy storage

Double-Fed Induction Generators (DFIG´s) driven by wind turbines are today the state of the art wind generators and are required to provide advanced functionalities in order to support the grid and comply with technical regulations. In this paper, we propose a novel control scheme for a wind turbine driven DFIG with an integrated energy storage. The control scheme is based on nonlinear control methods and provides three functionalities: a) maximum power point tracking (MPPT) during low range of wind speed conditions, b) power ouput smoothing (alleviating the effect of intermittency into the grid) and c) constant power output during variations of the mean wind speed and tracking of the committed power reference. Our approach involves first expressing the control objectives into asymptotic stability guarantees of desired equillibrium points and then mapping these guarantees to asymptotic stability of energy-level equilibrium points. We establish equivalence between the two, and then use shifted ectropy functions as Control Lyapunov Functions (CLF) to design the corresponding controllers. We demonstrate the performance of the proposed control scheme under critical scenarios on a 3-bus power system.