Abstract: A method and apparatus for deriving characteristics of a utility signal for synchronizing the output of a motor drive with the utility for a transfer or capture operation. With the drive in idle, the voltage and phase angle of an input to the drive are detected by instrumentation of the drive. The voltage and phase angle of a signal from a utility are detected by instrumentation of the drive at the output of the drive. A phase angle difference and scaling factor are determined to correlate the input signal to the motor drive with the signal at the output of the motor drive. The phase angle difference and scaling factor are stored and subsequently used to derive the signal at the motor due to the utility at the time of the transfer or capture procedure.

Abstract: A method and apparatus for switching an AC motor between two power supplies such as supply mains and a variable frequency AC motor drive. In a transfer procedure, the motor drive is coupled to the motor to power the motor. When the supply main is connected to the motor, a resulting current spike in the output of the motor drive is detected to disconnect the motor drive from the motor very quickly while limiting current. In a capture procedure, both power supplies are coupled to the motor with the motor drive in an idle mode. When the supply mains are disconnected from the motor, the voltage change in the output of the motor drive is detected to quickly activate the motor drive to power the motor.

Abstract: Stored rotational energy in an operating variable speed wind turbine is used to pitch blades and brake the wind turbine in the event of utility power grid failure. In one embodiment, a generator IGBT converter and the main power utility grid IGBT converter supply control and pitch servo power during turbine deceleration, and a ride-through capacitor on a DC emergency power supply bus and the main DC link capacitor provide additional energy storage. In another embodiment, a step-down DC/DC power converter adds to the intermediate DC link of the power conversion system with the secondary of the step down converter powering both the hub pitch controller and the wind turbine control system.