Frequency dependent strategy for mitigating wind power fluctuations of a doubly-fed induction generator wind turbine based on virtual inertia control and blade pitch angle regulation

This paper presents a new approach to address the issue of the frequency deviations induced by the fluctuating power injected into the grid by doubly-fed induction generator based wind turbines in a weak or isolated power system that is based in a frequency dependent smoothing of the wind power. An algorithm that allows an improved maximum power point tracking curve shifting as a function of the blade pitch angle variation has been proposed, taking advantage of the combined effect of two frequency control strategies: one based on the use of the stored kinetic energy by means of the concept of virtual inertia, and the other, by limiting the captured wind power through blade pitch angle regulation. This algorithm has been devised to reduce the turbine deload requirements, and at the same time, to increase the available kinetic energy in the turbine. This results in a more effective fast-frequency response with a lower amount of non-dispatched wind energy. The effectiveness of the proposed method is assessed by considering a real wind profile in time-domain simulations.