SIMPLE METHOD FOR ANALYZING THE DYNAMIC BEHAVIOUR OF INDUCTION MOTOR DRIVES CONTROLLED BY CURRENT SOURCE INVERTER.

A simplified analysis of the dynamic behavior of induction motors fed by current source inverters (CSI) is presented. The basic idea of the method is to approximate the theoretically rather complicated CSI by an ideal current source of fundamental harmonic. The approximation eliminates the two stator time constants. The induction motor has three energy storages in this simplified mathematical description, valid, however, only for the fundamental harmonic. By using Park vectors, the basic differential equations of the simplified system can easily be set up. Linearizing at small deviations, transfer functions can be determined between the motor torque and various control signals by using the superposition theorem. If the transfer functions are known, a simple block diagram provides a means for studying the system by classical control theory frequency method, root-locus method, etc. ). Stability criteria, for instance, can easily be derived both for open circuits and for feedback loops, and the control circuit parameters can also be estimated, etc. For the illustration of the described method the dynamic behavior is shown for different ways of control.