Adaptive control of variable speed wind turbines

This paper discusses the development of an adaptive feedback linearisation controller for a variable speed wind turbine. The controller provides an adaptive estimate of the turbine shaft torque. A feedback linearisation controller utilises the torque estimate to provide a torque reference for a field oriented squirrel cage induction machine. The induction machine is connected through a gearbox to the turbine shaft. The feedback linearisation controller ensures that a linear relationship is maintained between the turbine speed and an additional user defined input. The additional input is designed using linear control theory to provide stable error dynamics and speed tracking. The speed reference for the controller is a function of the wind speed and is chosen to ensure maximum energy capture from the wind for varying wind conditions. Simulation results demonstrate the effectiveness of such a controller in capturing maximum available energy from the wind.