Stability improvement of a round rotor synchronous machine by using an anisotropic control method

In this paper a fictitious and variable anisotrophy is induced in the three phase round rotor synchronous machine to enlarge the stability limits. Such result can be obtained by using suitable control loops acting simultaneously on the field windings of the d.c. excitation. The static round rotor synchronous machine behaviour is controlled by supplying the field winding in such a way that fictitious direct and quadrature synchronous reactances (X'd and X'q) are generated. The fictitious reactances can be automatically controlled and continuously regulated by varying the d.c. field excitation such that a resultant anisotropic torque can be obtained. The variable field action of the machine lets an enlargement of the stability bounds with respect to the conventional machines. Theoretical results and static behaviour of the new fictitious machine are presented