A Speed Range Extension Scheme for Induction Motor Drive with Open-end Stator Windings with Maximum Torque Per Ampere Control

Abstract

This paper presents a speed range extension scheme for induction motor drives with open-end stator windings having a DC source fed inverter at one end and a floating capacitor fed inverter at the other end. The Maximum Torque Per Ampere (MTPA) control scheme is used for speed control which ensures higher efficiency as compared to the conventional V/f and Field Oriented Control (FOC) schemes. In the proposed scheme, the capacitor fed inverter provides the reactive component of the higher voltage to be applied to the motor at higher speeds to overcome the increased back EMF. Hence, a higher speed range of operation can be realized with a given DC source voltage without resorting to field weakening. Thus, the capability of the motor to deliver rated torque is not compromised at higher speeds. The proposed scheme enhances the utilization of the DC source fed inverter as it is used only for supplying active power and the reactive power requirement is fully compensated by the capacitor fed inverter. This feature is specifically advantageous in applications like battery powered electric vehicles. The proposed scheme is validated by simulation and then experimentally verified on a laboratory prototype.