The Immersion and Invariance Wind Speed Estimator Revisited and New Results

The Immersion and Invariance (I&I) wind speed estimator is a powerful widely-used technique to estimate the rotor effective on horizontal axis turbines. Anyway, its global convergence proof rather cumbersome, which hinders extension of method time-delayed and/or uncertain systems. In this letter, we illustrate that circle criterion can be used as an alternative prove I\&I estimator. This also opens up inclusion time-delays uncertainties. First, demonstrate I&I equivalent torque balance with proportional correction term. As nonlinearity in sector bounded, well-known applied guarantee for By looking at theoretical framework from new perspective, letter further proposes addition integrator term improve performance. Case studies show proposed additional integral estimation. Furthermore, guaranteed by