REGULATION OF AN INDUCTION MOTOR UNDER BROAD CHANGES IN DC-LINK VOLTAGE

摘要

This paper deals with the control of an induction motor (IM) fed from a voltage source inverter (VSI) under conditions of a wide range and rapid changes in the DC-link voltage. Uncontrollable transients can arise in the IM due to a rapid voltage drop in the DC link. Two techniques which substantially increase the robustness of the IM control system under these rugged operating conditions are discussed in detail. They are the IM field-weakening and the IM torque limitation in case of the DC-link voltage drop. The field-weakening is studied in detail for the IM stator flux vector control method (SFVC). A simplification of the field-weakening structure has been designed with the use of the operating point trajectory analysis in a plane defined by stator flux space vector coordinates. In addition, an innovation of the maximum stator current limitation during IM field-weakening has been designed. We worked out a new control structure for the IM torque limitation based on the drive power balance. All mentioned solutions are theoretically discussed in detail and verified by computer simulations in the time domain and also by practical experiments with an 85 kW AC drive model.