General method of magnetising flux saturation modelling in d-q axis models of double-cage induction machines

Two models of induction machines with two rotor windings, that include magnetising flux saturation, are available at present: the first one is the current state-space model, where state-space variables are selected as d-q axis components of stator and both rotor currents, while in the second model state-space variables are d-q axis components of stator and both rotor flux linkages. The paper presents a general procedure for inclusion of magnetising flux saturation in d-q axis model of induction machines with two rotor windings. Using the procedure it becomes possible to derive a model of a saturated induction machine with two rotor windings for any selected set of state-space variables. The approach to magnetising flux saturation modelling relies on the concept of 'generalised flux space vector', which has recently been introduced for single-cage induction machines. Several characteristic models of a saturated induction machine, derived by applying the concept of the generalised flux space vector, are presented in detail. In order to verify the models, an extensive simulation study of double-cage induction generator self-excitation process is performed, accompanied by the corresponding experimental investigation. The main results of the study are included. Finally, advantages of some of the novel models over the existing ones and possible applications are addressed.