Rotational speed characteristics of load torque to extend the operable tip speed ratio range for fixed pitch wind turbines

This study explored the effective operational range of fixed pitch wind turbines by focusing on extending the lower end of tip speed ratios. We investigated how these kinds of wind turbines perform under higher-than-rated wind speeds by analysing the load torque characteristics of the generator using numerical and mathematical methods. The core analysis involved non-dimensional governing equations, assessing the variation of the aerodynamic
torque coefficient as a function of the tip speed ratio. Utilising data from two previous studies, the distribution of aerodynamic torque coefficients is detailed, and the fourth-order Runge-Kutta method is applied to numerically analyse the impact of load torque characteristics on turbine rotational behaviours. Further, the tip speed ratio changes from the optimal value under constant and linear load torque conditions were examined. Results indicate that under constant load, the tip speed ratio approaches zero below a critical ratio and stabilises above it. Under linear conditions, this critical ratio diminishes, broadening the operational range. The study proposes and validates novel equations for the critical tip speed ratio, highlighting the benefits of linear load torque adjustments that could enhance wind turbines’ performance and efficiency.