INVESTIGATION OF A WOUND ROTOR INDUCTION GENERATOR WITH STATOR AND ROTOR WINDINGS CONNECTED IN SERIES THROUGH A FREQUENCY CONVERTER

Abstract

The article describes the working processes in a new version of the generating set comprising a wound-rotor induction machine, the stator and rotor windings in which are connected in series via a rectifier and an inverter, which operates at a rotation speed higher than the synchronous one. This generator set provides a stable output voltage frequency at variable speed; in other words, it belongs to the class of "variable speed - constant frequency" systems. Owing to series connection of the stator and rotor windings, stable running of the system is achieved in overcurrent modes of operation. With such connection arrangement, the induction machine stator windings also behave as a filter, due to which a low output voltage harmonic distortion factor is obtained. In accordance with modern approaches to investigation of new technical solutions, it is necessary to create a model describing a six-terminal wound-rotor induction machine. The working processes in the generator set are studied with the help of computer simulation in the Orcad PSpice software package. A model of wound rotor induction machine itself was developed in the PSpice program input language. The model involves the well-known mathematical description of a three-phase electrical machine in the untransformed coordinate system taking into account the magnetic core saturation. The model does not take toothed curvature of stator and rotor packet, mechanical loss, and iron loss. The article presents the results of verifying the developed model of a wound rotor induction machine with for adequacy in the generator and motor mode of its operation. Comparison of the simulation results with the known theoretical statements demonstrated the possibility of using the model for carrying out investigations in the generator and motor modes. The developed model can be used as a library element of the selected simulation program. The proposed generating set version was studied in the autonomous mode and during its parallel operation with the network using the above-mentioned model. The study results are summarized in the form of tables and oscillograms. Wind power and hydropower are potential application fields of the proposed generating set version.