Steady state analysis and experimental investigation of a doubly-fed induction machine supplied by a `current-source´ cycloconverter in the rotor

The doubly-fed induction machine (DFIM) has taken increasing importance for variable speed drives due to the progress of field oriented control. It is an induction machine supplied by AC mains on the stator side and controlled from the rotor side by changing the magnitude, frequency and phase of the rotor voltage or current. It can operate as well as a motor or a generator and its speed may be both subsynchronous and supersynchronous. The authors present a steady state analysis of a DFIM supplied by a `current-source´ cycloconverter (CSC) in the rotor. A mathematical model is presented in vectorial representation. The expressions of various output variables are developed and the effect of the control parameters are investigated for every mode of operation. The performances of the drive are determined analytically in steady state and confirmed by measurements. Limitations in the operation are determined by the limits of currents that the machine can carry and the stability problem