Optimal torque control based on effective tracking range for maximum power point tracking of wind turbines under varying wind conditions

Abstract

This study focuses on the development of optimal torque (OT) control, which is a commonly used method for maximum power point tracking (MPPT). Due to the sluggish response of wind turbines with high inertia, conventional OT control was improved to increase MPPT efficiency by dynamically modifying the generator torque versus rotor speed curve. An idea that tracking a local interval of wind speed where the wind energy is primarily distributed rather than the total range of wind speed variation is applied in this study. On this basis, an effective tracking range (ETR) that corresponds to the local interval of wind speed with concentrated wind energy distribution is proposed and an improved OT control based on ETR is developed. In this method, based on a direct relationship between ETR and wind conditions, the torque curve can be quickly optimised so that higher and more stable MPPT efficiency can be achieved under varying wind conditions. Meanwhile, MPPT efficiency enhancement by reducing tracking range without increasing torque discrepancy leads to a low cost of generator torque fluctuation and drive train load. Finally, simulations based on fatigue, aerodynamics, structures, and turbulence (FAST) code and experiments conducted on a wind turbine simulator are presented to verify the proposed method.