Abstract: A method for controlling a rotational speed of a rotor having at least one rotor blade, a rotor shaft, and an electrical generator coupled thereto. The method includes controlling a torque of the rotor shaft by controlling a torque of the electrical generator, alternating between changing an angle of pitch of the at least one rotor blade and maintaining the angle of pitch of the at least one rotor blade substantially constant, and maintaining a substantially constant rotational speed of the rotor during variable wind speeds above a predetermined rated wind speed.

Abstract: A variable speed wind turbine employing a rotor connected to a multiplicity of synchronous generators with wound field or permanent magnet rotors. A passive rectifier and an inverter are used for power transfer back to the grid. A Turbine Control Unit (TCU) commands a required generator torque based on rotor speed and power output of the turbine inverters. Torque is controlled by regulating the DC current by control of the inverter. A main-shaft-damping filter is provided by measurement of the DC bus voltage. In high winds the turbine remains at a constant average output power through a constant torque command and a varying pitch command to a rotor pitch servo system. A set point is fixed at the inverter output such that output VAR load is minimized running the turbine at very nearly unity power factor. Dynamic VAR and power factor control is provided by a separate VAR apparatus.

Abstract: A variable speed system for use in systems, such as, for example, wind turbines, is described. The system comprises a wound rotor induction generator, a torque controller and a proportional, integral derivative (PID) pitch controller. The torque controller controls generator torque using field oriented control, and the PID controller performs pitch regulation based on generator rotor speed.

Abstract: A variable speed wind turbine employing a rotor connected to a multiplicity of synchronous generators with wound field or permanent magnet rotors. A passive rectifier and an inverter are used for power transfer back to the grid. A Turbine Control Unit (TCU) commands a required generator torque based on rotor speed and power output of the turbine inverters. Torque is controlled by regulating the DC current by control of the inverter. A main-shaft-damping filter is provided by measurement of the DC bus voltage. In high winds the turbine remains at a constant average output power through a constant torque command and a varying pitch command to a rotor pitch servo system. A set point is fixed at the inverter output such that output VAR load is minimized running the turbine at very nearly unity power factor. Dynamic VAR and power factor control is provided by a separate VAR apparatus.