Control of a Five-Phase Induction Motor Drive with High-Torque Density and Voltage Overmodulation

The torque density of a multiphase motor can be increased without exceeding the current limit of the drive if the high-order spatial harmonics of the magnetic field in the air gap are appropriately synchronized with the fundamental one. However, this method is feasible only if the rotor speed is below the base speed because of the limited voltage of the converter. In fact, as the speed increases, the voltage required to sustain the harmonics of the field in the air gap rises. Above a certain speed, the most used strategy consists of controlling only the fundamental component of the magnetic field in the airgap. This paper shows that motor performance can improve if the injection of voltage harmonics is used to extend the linear modulation range of the fundamental component of the voltage vector. In the field weakening region, an increase in the magnitude of the stator voltage vector improves the motor power and torque. Experimental tests on a five-phase induction motor drive confirm the feasibility and the effectiveness of the developed control scheme.