Variable Speed-Variable Pitch Controllers for Aero-Servo-Elastic Simulations of Wind Turbine Support Structures

Abstract

Fatigue loads, which affect design of support structures of wind turbines, are strongly dependent on controllers. Variable speed - variable pitch controller of typical wind turbines were formulated considering characteristics of wind turbines such as rotors, towers, and control system. In succession, pitch and torque PI controllers, which are compatible for fatigue loads of tower and blades as well as pitch rate, were investigated through case studies. Optimum pitch controllers were shown to be dependent on tower vibration. Gain cross frequencies of pitch controllers were recommended to be about 20% of first mode bending frequency of wind turbines. Furthermore, gain scheduling was shown to improve the characteristics.