Steady-state and stability analysis of a doubly-fed asynchronous machine supplied by a current controlled cycloconverter

The authors present a steady-state investigation of a doubly fed asynchronous machine (DFAM) supplied by a current-controlled cycloconverter (CCC) in the rotor and AC mains in the stator. The model of the DFAM is based on a space vector representation. A theoretical analysis and the characteristics at constant torque are presented. The DFAM is shown to behave like a nonsalient synchronous machine, and the exciting and stator currents are homologous in both machines. The analogy is confirmed by the stator-rotor current characteristics at constant torque and the reactive power flow in the DFAM. The transient performances and the dynamic stability are also analyzed. A stability investigation on a test machine shows the simplicity of the transfer function. For any perturbation, the system can be approximated by a second degree polynomial and is stable within a wide range of the load angle