Torque control of yawing of a constant speed two-bladed wind turbine with passive cyclic pitch variation.

The paper summarizes from continued analysis supported atmospheric testing of two-bladed 7.6 m diameter upwind vane stabilized wind turbine with passive cyclic pitch variation. The previously used variable speed alternator was replaced by a utility grid connected induction generator of nearly constant speed. The purely mechanical passive yaw control system was retained. The control system limited rotor torque, prevented blade stall and at high wind speed lowered the generator speed below synchronous so that power was cut out by the generator speed switch. Wind switches, mechanical or aerodynamic rotor brakes and control actuators were avoided. The paper includes analytical and test data on the effects of turbulence and of blade stall on the performance and controls.