Small Signal Dynamic Analysis of Regeneration and Self-Excitation in Induction Machines

Small signal stability and dynamic response is examined and compared for six modes of source-connected and self-excited induction generator operation including both voltage (VSI) and current (CSI) inverter systems. It is shown that conventional small signal machine modelling is incapable of yielding any information whatsoever concerning the stability of self-excitation at constant speed. A recently introduced small signal model which includes main flux saturation overcomes these difficulties and is employed to study the stability properties of all six modes. General stability and dynamic response properties of each mode are summarized and compared, especially with respect to the influence of saturation. The capacitive self-excited case is shown to require special treatment because of the phase freedom inherent in this mode. Experimental confirmation of some of the results is included.