Patent 8076874 was granted and assigned to Hitachi on December, 2011 by the United States Patent and Trademark Office.
A motor is controlled to always consume power supplied from a power supply system or not to supply power to the power supply system, by performing control to advance or delay a phase of a 3-phase current flowing in the motor or to reduce a percentage of the generated torque with respect to an effective value of the 3-phase current of the motor, or by applying a d-axis current to the motor.