Novel voltage trajectory control for field weakening operation of induction motor drives

This paper proposes a new voltage trajectory control for field weakening operation of induction motor drives. The presented method doesn´t require look-up-table and reduces the parameter sensitivity. Moreover, the DC-link voltage can be fully utilized such that the voltage moves along the hexagon trajectory of space vector of voltage. The difference between the switching period and summation of active switching times for inverter PWM control is used for field weakening control. As the summation of active switching times less than its switching period, constant torque is retained. In contrast, field weakening control is considered. Smooth and automatic transition between two field weakening regions can be achieved by the calculated q-axis current subjected to the voltage, current and maximum pull-out torque constraints. Experimental and simulation results will be presented to fully support the claims.