Derrieus wind turbine electric generating system

In an electric generating system of the type to be connected to a power grid carrying current of preselected frequency and phase, and to supply power to and receive power from the grid, and designed to operate with a wind turbine prime mover having negligible starting torque, the combination of

• (a) a support on which the turbine can be mounted;
• (b) a clutch having an input shaft for connection to the turbine shaft and an output shaft, and having an overriding mode permitting the transfer of torque from the input shaft to the output shaft and preventing the transfer of torque from the output shaft to the input shaft, said clutch entering its overriding mode responsive to a first level of a clutch control signal, said clutch also having a lockup mode wherein torque from the output shaft can be transferred to the input shaft, said clutch entering its lockup mode responsive to a second level of the clutch control signal;
• (c) A generator mounted on the support and whose rotor is connected to rotate with the clutch output shaft, and having output terminals for providing electric power to the grid when torque is applied to the rotor, said generator also functioning as a motor and supplying torque to the clutch output shaft responsive to the combination of absence of torque to the rotor from the clutch output shaft and current input to the generator output terminals;
• (d) an anemometer mounted adjacent the wind turbine support and producing a wind strength signal having a first level indicative of wind below a predetermined threshold speed, and a second level indicative of wind at or above the threshold speed;
• (e) turbine operating condition indicating means sensing whether the turbine is rotating, for supplying a turbine speed signal having a first level responsive to the turbine having rotational speed above a predetermined level, and a second level otherwise;
• and
• (f) start-up control means receiving the turbine speed signal and the wind strength signals, for supplying a clutch control signal having its second level for at least a predetermined interval responsive to the wind strength signal falling within its second level when the turbine speed signal is at its second level, and supplying a clutch control signal having its first level otherwise.