Operating a brushless doubly fed machine (BDFM) to enable a unidirectional power flow from an AC mains power supply line

摘要

A BDFM comprises a brushless doubly fed generator (BDFG) having a rotor, a power stator winding and a control stator winding, said rotor having a natural speed of rotation. The operating method comprising reducing an efficiency of the BDFM above its natural speed of rotation by driving power into said control stator winding above said natural speed of rotation to increase losses in said machine. Preferably driving power into the control stator winding comprises driving the control stator winding with a voltage greater than a voltage defined by a speed of rotation of said rotor, the natural speed of rotation of said rotor and a characteristic curve of the machine. The method may also comprise compensating for increased reactive power from said power stator winding due to said driving of said control stator winding with an increased voltage. This operating method finds particular application with wind turbines that are subject to gusts of wind.