Dynamic wind estimation based control for small wind turbines

We introduce a novel scheme for small wind turbines that gives dynamic estimation of wind speed from rotor angular velocity measurements. The estimation proceeds in two different dynamic observers, one giving a valid estimate for higher Tip Speed Ratios (TSRs) and which we call the Upper Wind Estimator (UWE) and the other called the Lower Wind Estimator (LWE) valid for lower TSRs. The meaning of “higher” and “lower”, and the precise regions of validity, are quantified. We further propose a coordinated control scheme using the UWE. Simulations are presented showing closed-loop performance of the turbine and the estimators both in the optimal TSR regulation condition, and the dynamic power-shedding condition caused by a wind gust. An analytic analysis of closed-loop stability and of the convergence and bias properties of the estimator is provided. Empirical data showing performance on a real turbine is also presented.

► Dynamic, not static scheme for estimation of wind speed from rotor angular velocity measurements for small turbines.
► Proposed coordinated Region II/Region III control law using estimators.
► Proof of asymptotic stability (shows regulation to correct TSR and unbiased, convergent wind speed estimate).
► Extensive simulations showing features/strength/weaknesses/points of material.
► Empirical data and experience presented.
►  Clearly written; easy to follow!