Variable-characteristic synchronous machines

The paper deals with the operation of a standard cylindrical-rotor synchronous machine with several novel forms of excitation control. It shows how, by using a nonlinear function of load-angle control, the machine can be made to develop characteristics normally associated with a salient-pole machine, and how a very wide range of the effective ratio of direct-axis to quadrature-axis synchronous reactances can be produced. Alternative control functions, designed to produce a machine with infinite stiffness, or with tangential forms of power/load-angle characteristics, are also described. Possible applications in large power systems, local generating plant and synchronous motor control are discussed.